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Cisco Security Advisory: Crafted TCP Packet Can Cause Denial of Service

Advisory ID: cisco-sa-20070124-crafted-tcp

http://www.cisco.com/warp/public/707/cisco-sa-20070124-crafted-tcp.shtml

Revision 1.0

For Public Release 2007 January 24 1600 UTC (GMT)

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Summary =======

The Cisco IOS Transmission Control Protocol (TCP) listener in certain versions of Cisco IOS software is vulnerable to a remotely-exploitable memory leak that may lead to a denial of service condition.

This vulnerability only applies to traffic destined to the Cisco IOS device. Traffic transiting the Cisco IOS device will not trigger this vulnerability.

Cisco has made free software available to address this vulnerability for affected customers.

This issue is documented as Cisco bug ID CSCek37177.

There are workarounds available to mitigate the effects of the vulnerability.

This advisory is posted at http://www.cisco.com/warp/public/707/cisco-sa-20070124-crafted-tcp.shtml

Affected Products =================

Vulnerable Products +------------------

This issue affects all Cisco devices running Cisco IOS software. To be affected, devices must be configured to process Internet Protocol version 4 (IPv4) packets and receive TCP packets. Devices which run only Internet Protocol version 6 (IPv6) are not affected.

This vulnerability is present in all unfixed versions of Cisco IOS software, including versions 9.x, 10.x, 11.x and 12.x.

To determine the software running on a Cisco product, log in to the device and issue the "show version" command to display the system banner. Cisco IOS software will identify itself as "Internetwork Operating System Software" or simply "IOS". On the next line of output, the image name will be displayed between parentheses, followed by "Version" and the IOS release name. Other Cisco devices will not have the "show version" command or will give different output.

The following example identifies a Cisco product running Cisco IOS release 12.2(14)S16 with an installed image name of C7200-IS-M:

Cisco Internetwork Operating System Software IOS (tm) 7200 Software (C7200-IS-M), Version 12.2(14)S16, RELEASE SOFTWARE (fc1)

The release train label is "12.2".

The next example shows a product running IOS release 12.3(7)T12 with an image name of C7200-IK9S-M:

Cisco IOS Software, 7200 Software (C7200-IK9S-M), Version 12.3(7)T12, RELEASE SOFTWARE (fc1)

Additional information about Cisco IOS Banners is available at:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_white_paper0...

Products Confirmed Not Vulnerable +-------------------------------- Cisco products that do not run IOS are unaffected by this vulnerability.

Cisco IOS-XR is not affected.

No other Cisco products are currently known to be affected by this vulnerability.

Details =======

TCP is the transport layer protocol designed to provide connection-oriented, reliable delivery of a data stream. To accomplish this, TCP uses a mixture of flags to indicate state and sequence numbers to identify the order in which the packets are to be reassembled. TCP also provides a number, called an acknowledgement number, that is used to indicate the sequence number of the next packet expected. The full specification of the TCP protocol can be found at http://www.ietf.org/rfc/rfc0793.txt

Cisco IOS devices that are configured to receive TCP packets are exposed to this issue. This Advisory does not apply to traffic that is transiting the device.

Certain crafted packets destined to an IPv4 address assigned to a physical or virtual interface on a Cisco IOS device may cause the device to leak a small amount of memory. Over time, such a memory leak may lead to memory exhaustion and potentially degraded service.

Although this is an issue with TCP, it is not required to complete the TCP 3-way handshake in order for the memory leak to be triggered. Therefore, TCP packets with a spoofed source address may trigger the leak.

The following document contains additional information on how to identify if your router is suffering from a memory leak in Processor memory:

http://www.cisco.com/warp/public/63/mallocfail.shtml#tshoot2

Vulnerability Scoring Details =============================

Cisco is providing scores for the vulnerabilities in this advisory based on the Common Vulnerability Scoring System (CVSS). Cisco will provide a base and temporal score. Customers can then compute environmental scores to assist in determining the impact of the vulnerability in individual networks.

Cisco PSIRT will set the bias in all cases to normal. Customers are encouraged to apply the bias parameter when determining the environmental impact of a particular vulnerability.

CVSS is a standards based scoring method that conveys vulnerability severity and helps determine urgency and priority of response.

Cisco has provided an FAQ to answer additional questions regarding CVSS at:

http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html

Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks: http://intellishield.cisco.com/security/alertmanager/cvss

Cisco Bug IDs:

CSCek37177

CVSS Base Score: 3.3 Access Vector: Remote Access Complexity: Low Authentication: Not Required Confidentiality Impact: None Integrity Impact: None Availability Impact: Complete Impact Bias: Normal

CVSS Temporal Score: 2.7 Exploitability: Functional Remediation Level: Official Fix Report Confidence: Confirmed

Impact ======

Successful exploitation of the vulnerability may result in a small amount of processor memory to leak, which may lead to degraded service. This issue will not resolve over time, and will require a device reset to recover the leaked memory.

This vulnerability only applies to traffic destined to the Cisco IOS device. Traffic transiting the device will not trigger this issue.

Software Version and Fixes ==========================

When considering software upgrades, also consult http://www.cisco.com/go/psirt and any subsequent advisories to determine exposure and a complete upgrade solution.

In all cases, customers should exercise caution to be certain the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, contact the Cisco Technical Assistance Center ("TAC") or your contracted maintenance provider for assistance.

Each row of the Cisco IOS software table (below) describes a release train and the platforms or products for which it is intended. If a given release train is vulnerable, then the earliest possible releases that contain the fix (the "First Fixed Release") and the anticipated date of availability for each are listed in the "Rebuild" and "Maintenance" columns. A device running a release in the given train that is earlier than the release in a specific column (less than the First Fixed Release) is known to be vulnerable. The release should be upgraded at least to the indicated release or a later version (greater than or equal to the First Fixed Release label).

For more information on the terms "Rebuild" and "Maintenance," consult the following URL:

http://www.cisco.com/warp/public/620/1.html

+------------------------------------------------------------------------+ | Major | Availability of Repaired Releases | | Release | | |------------+-----------------------------------------------------------| | Affected | | | | 12.0-Based | Rebuild | Maintenance | | Release | | | |------------+-----------------------------------------------------------| | 12.0 | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0DA | Vulnerable; migrate to 12.2(10)DA5 or later | |------------+-----------------------------------------------------------| | 12.0DB | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.0DC | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | | 12.0(31)S6 | | |12.0S |----------------------------+------------------------------| | | 12.0(32)S4 | | |------------+-----------------------------------------------------------| | 12.0SC | Vulnerable; migrate to 12.3(13a)BC6 or later | |------------+-----------------------------------------------------------| | 12.0SL | Vulnerable; migrate to 12.0(31)S6 or later | |------------+-----------------------------------------------------------| | 12.0SP | Vulnerable; migrate to 12.0(31)S6 or later | |------------+-----------------------------------------------------------| | 12.0ST | Vulnerable; migrate to 12.0(31)S6 or later | |------------+-----------------------------------------------------------| | 12.0SX | 12.0(25)SX11 | | |------------+----------------------------+------------------------------| | 12.0SY | | 12.0(32)SY | |------------+-----------------------------------------------------------| | 12.0SZ | Vulnerable; migrate to 12.0(31)S6 or later | |------------+-----------------------------------------------------------| | 12.0T | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0W | Not vulnerable | |------------+-----------------------------------------------------------| | 12.0WC | 12.0(5)WC15 | | |------------+-----------------------------------------------------------| | 12.0WT | Not vulnerable | |------------+-----------------------------------------------------------| | 12.0XA | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XB | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XC | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XD | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XE | Vulnerable; migrate to 12.1(26)E7 or later | |------------+-----------------------------------------------------------| | 12.0XF | Not vulnerable | |------------+-----------------------------------------------------------| | 12.0XG | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XH | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XI | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XJ | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XK | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XL | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XM | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XN | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XQ | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XR | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XS | Vulnerable; migrate to 12.1(26)E7 or later | |------------+-----------------------------------------------------------| | 12.0XV | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.0XW | Not vulnerable | |------------+-----------------------------------------------------------| | Affected | | | | 12.1-Based | Rebuild | Maintenance | | Release | | | |------------+-----------------------------------------------------------| | 12.1 | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1 AA | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1 AX | Vulnerable; migrate to 12.2(25)EY4 or later | |------------+-----------------------------------------------------------| | 12.1 AY | Vulnerable; migrate to 12.1(22)EA8 or later | |------------+-----------------------------------------------------------| | 12.1 AZ | Vulnerable; migrate to 12.1(22)EA8 or later | |------------+-----------------------------------------------------------| | 12.1 CX | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1 DA | Vulnerable; migrate to 12.2(10)DA5 or later | |------------+-----------------------------------------------------------| | 12.1 DB | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.1 DC | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | | 12.1(26)E7 | | |12.1E |----------------------------+------------------------------| | | 12.1(27b)E1 | | |------------+----------------------------+------------------------------| | 12.1EA | 12.1(22)EA8 | | |------------+-----------------------------------------------------------| | 12.1EB | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.1EC | Vulnerable; migrate to 12.3(13a)BC6 or later | |------------+-----------------------------------------------------------| | | 12.1(19)EO6; available on | | | 12.1EO | 31-Jan-07 | | | |----------------------------+------------------------------| | | 12.1(20)EO3 | | |------------+-----------------------------------------------------------| | 12.1EU | Vulnerable; migrate to 12.2(25)EWA6 or later | |------------+-----------------------------------------------------------| | 12.1EV | Vulnerable; migrate to 12.2(27)SV4 or later | |------------+-----------------------------------------------------------| | 12.1EW | Vulnerable; migrate to 12.2(25)EWA6 or later | |------------+-----------------------------------------------------------| | 12.1EX | Vulnerable; migrate to 12.1(26)E7 or later | |------------+-----------------------------------------------------------| | 12.1EY | Vulnerable; migrate to 12.1(26)E7 or later | |------------+-----------------------------------------------------------| | 12.1EZ | Vulnerable; migrate to 12.1(26)E7 or later | |------------+-----------------------------------------------------------| | 12.1T | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1XA | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1XB | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1XC | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1XD | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1XE | Vulnerable; migrate to 12.1(26)E7 or later | |------------+-----------------------------------------------------------| | 12.1XF | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1XG | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1XH | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1XI | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1XJ | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1XL | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1XM | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1XP | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1XQ | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1XR | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1XS | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1XT | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1XU | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1XV | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1XW | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1XX | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1XY | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1XZ | Vulnerable; migrate to 12.2(37) or later | |------------+-----------------------------------------------------------| | 12.1YA | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1YB | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1YC | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1YD | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1YE | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1YF | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1YH | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1YI | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.1YJ | Vulnerable; migrate to 12.1(22)EA8 or later | |------------+-----------------------------------------------------------| | Affected | | | | 12.2-Based | Rebuild | Maintenance | | Release | | | |------------+----------------------------+------------------------------| | 12.2 | | 12.2(37) | |------------+-----------------------------------------------------------| | 12.2B | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2BC | Vulnerable; migrate to 12.3(13a)BC6 or later | |------------+-----------------------------------------------------------| | 12.2BW | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2BY | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2BZ | Vulnerable; migrate to 12.3(7)XI8 or later | |------------+-----------------------------------------------------------| | 12.2CX | Vulnerable; migrate to 12.3(13a)BC6 or later | |------------+-----------------------------------------------------------| | 12.2CY | Vulnerable; migrate to 12.3(13a)BC6 or later | |------------+-----------------------------------------------------------| | 12.2CZ | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | | 12.2(10)DA5 | | |12.2DA |----------------------------+------------------------------| | | 12.2(12)DA10 | | |------------+-----------------------------------------------------------| | 12.2DD | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2DX | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2EU | Vulnerable; migrate to 12.2(25)EWA6 or later | |------------+-----------------------------------------------------------| | 12.2EW | Vulnerable; migrate to 12.2(25)EWA6 or later | |------------+-----------------------------------------------------------| | 12.2EWA | 12.2(25)EWA6 | | |------------+----------------------------+------------------------------| | 12.2EX | 12.2(25)EX1 | | |------------+----------------------------+------------------------------| | 12.2EY | 12.2(25)EY4 | | |------------+-----------------------------------------------------------| | 12.2EZ | Vulnerable; migrate to 12.2(25)SEE1 or later | |------------+-----------------------------------------------------------| | 12.2FX | Vulnerable; migrate to 12.2(25)SEE1 or later | |------------+-----------------------------------------------------------| | 12.2FY | Vulnerable; migrate to 12.2(25)SEE1 or later | |------------+-----------------------------------------------------------| | 12.2FZ | All 12.2FZ releases are fixed | |------------+-----------------------------------------------------------| | 12.2IXA | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.2IXB | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.2IXC | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.2JA | Vulnerable; migrate to 12.3(8)JA2 or later | |------------+-----------------------------------------------------------| | 12.2JK | Vulnerable; migrate to 12.4(4)T4 or later | |------------+-----------------------------------------------------------| | 12.2MB | Vulnerable; migrate to 12.2(25)SW8 or later | |------------+-----------------------------------------------------------| | 12.2MC | Vulnerable; migrate to 12.3(11)T11 or later | |------------+-----------------------------------------------------------| | 12.2S | 12.2(25)S12; Available | | | | 12-Feb-07 | | |------------+----------------------------+------------------------------| | 12.2SB | 12.2(28)SB2 | 12.2(31)SB | |------------+----------------------------+------------------------------| | 12.2SBC | 12.2(27)SBC5 | | |------------+----------------------------+------------------------------| | 12.2SE | | 12.2(35)SE | |------------+-----------------------------------------------------------| | 12.2SEA | Vulnerable; migrate to 12.2(25)SEE1 or later | |------------+-----------------------------------------------------------| | 12.2SEB | Vulnerable; migrate to 12.2(25)SEE1 or later | |------------+-----------------------------------------------------------| | 12.2SEC | Vulnerable; migrate to 12.2(25)SEE1 or later | |------------+-----------------------------------------------------------| | 12.2SED | Vulnerable; migrate to 12.2(25)SEE1 or later | |------------+-----------------------------------------------------------| | 12.2SEE | 12.2(25)SEE1 | | |------------+----------------------------+------------------------------| | 12.2SEF | 12.2(25)SEF1 | | |------------+-----------------------------------------------------------| | 12.2SEG | All 12.2SEG releases are fixed | |------------+-----------------------------------------------------------| | 12.2SG | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.2SGA | All 12.2SGA releases are fixed | |------------+-----------------------------------------------------------| | 12.2SO | 12.2(18)SO7 | | |------------+-----------------------------------------------------------| | 12.2SRA | All 12.2SRA releases are fixed | |------------+-----------------------------------------------------------| | 12.2SRB | All 12.2SRB releases are fixed | |------------+-----------------------------------------------------------| | 12.2SU | Vulnerable; migrate to 12.4(8) or later | |------------+-----------------------------------------------------------| | | 12.2(27)SV4 | | | |----------------------------+------------------------------| | 12.2SV | 12.2(28)SV1 | | | |----------------------------+------------------------------| | | 12.2(29)SV1 | | |------------+----------------------------+------------------------------| | 12.2SW | 12.2(25)SW8 | | |------------+-----------------------------------------------------------| | 12.2SX | Vulnerable; migrate to 12.2(18)SXD7a or later | |------------+-----------------------------------------------------------| | 12.2SXA | Vulnerable; migrate to 12.2(18)SXD7a or later | |------------+-----------------------------------------------------------| | 12.2SXB | Vulnerable; migrate to 12.2(18)SXD7a or later | |------------+-----------------------------------------------------------| | 12.2SXD | 12.2(18)SXD7a | | |------------+----------------------------+------------------------------| | 12.2SXE | 12.2(18)SXE6 | | |------------+----------------------------+------------------------------| | 12.2SXF | 12.2(18)SXF5 | | |------------+-----------------------------------------------------------| | 12.2SY | Vulnerable; migrate to 12.2(18)SXD7a or later | |------------+-----------------------------------------------------------| | 12.2SZ | Vulnerable; migrate to 12.2(25)S12 or later; Available | | | 12-Feb-07 | |------------+-----------------------------------------------------------| | 12.2T | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2TPC | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.2XA | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XB | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XC | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2XD | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XE | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XF | Vulnerable; migrate to 12.3(13a)BC6 or later | |------------+-----------------------------------------------------------| | 12.2XG | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XH | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XI | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XJ | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XK | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XL | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XM | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XN | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XQ | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XR | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XS | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XT | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XU | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XV | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2XW | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2YA | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2YB | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2YC | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2YD | Vulnerable; migrate to 12.3(11)T11 or later | |------------+-----------------------------------------------------------| | 12.2YE | Vulnerable; migrate to 12.2(25)S12 or later; Available | | | 12-Feb-07 | |------------+-----------------------------------------------------------| | 12.2YF | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2YG | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2YH | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2YJ | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2YK | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2YL | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2YM | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2YN | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2YO | Not vulnerable | |------------+-----------------------------------------------------------| | 12.2YP | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2YQ | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2YR | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2YS | Not vulnerable | |------------+-----------------------------------------------------------| | 12.2YT | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2YU | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2YV | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2YW | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2YX | Vulnerable; migrate to 12.4(8) or later | |------------+-----------------------------------------------------------| | 12.2YY | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2YZ | Vulnerable; migrate to 12.2(25)S12 or later; Available | | | 12-Feb-07 | |------------+-----------------------------------------------------------| | 12.2ZA | Vulnerable; migrate to 12.2(18)SXD7a or later | |------------+-----------------------------------------------------------| | 12.2ZB | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2ZC | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2ZD | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.2ZE | Vulnerable; migrate to 12.3(19) or later | |------------+-----------------------------------------------------------| | 12.2ZF | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2ZG | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.2ZH | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.2ZJ | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2ZL | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.2ZN | Vulnerable; migrate to 12.3(4)T13 or later | |------------+-----------------------------------------------------------| | 12.2ZP | Vulnerable; migrate to 12.4(8) or later | |------------+-----------------------------------------------------------| | Affected | | | | 12.3-Based | Rebuild | Maintenance | | Release | | | |------------+----------------------------+------------------------------| | 12.3 | 12.3(10f) | 12.3(19) | |------------+-----------------------------------------------------------| | 12.3B | Vulnerable; migrate to 12.3(11)T11 or later | |------------+-----------------------------------------------------------| | | 12.3(13a)BC6 | | |12.3BC |----------------------------+------------------------------| | | 12.3(17a)BC2 | | |------------+-----------------------------------------------------------| | 12.3BW | Vulnerable; migrate to 13.3(11)T11 or later | |------------+-----------------------------------------------------------| | 12.3JA | 12.3(8)JA2 | | |------------+-----------------------------------------------------------| | 12.3JEA | All 12.3JEA releases are fixed | |------------+-----------------------------------------------------------| | 12.3JEB | All 12.3JEB releases are fixed | |------------+-----------------------------------------------------------| | 12.3JK | 12.3(2)JK2 | | |------------+----------------------------+------------------------------| | 12.3JX | 12.3(7)JX4 | 12.3(11)JX | |------------+----------------------------+------------------------------| | | 12.3(4)T13 | | |12.3T |----------------------------+------------------------------| | | 12.3(11)T11 | | |------------+-----------------------------------------------------------| | 12.3TPC | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.3XA | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.3XB | Vulnerable; migrate to 12.3(11)T11 or later | |------------+-----------------------------------------------------------| | 12.3XC | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.3XD | Vulnerable; migrate to 12.3(11)T11 or later | |------------+-----------------------------------------------------------| | 12.3XE | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.3XF | Vulnerable; migrate to 12.3(11)T11 or later | |------------+-----------------------------------------------------------| | 12.3XG | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.3XH | Vulnerable; migrate to 12.3(11)T11 or later | |------------+-----------------------------------------------------------| | 12.3XI | 12.3(7)XI8 | | |------------+-----------------------------------------------------------| | 12.3XJ | Vulnerable; migrate to 12.3(14)YX2 or later | |------------+-----------------------------------------------------------| | 12.3XK | Vulnerable; migrate to 12.4(8) or later | |------------+-----------------------------------------------------------| | 12.3XQ | Vulnerable; migrate to 12.4(8) or later | |------------+-----------------------------------------------------------| | 12.3XR | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.3XS | Vulnerable; migrate to 12.4(8) or later | |------------+-----------------------------------------------------------| | 12.3XU | Vulnerable; migrate to 12.4(2)T5 or later | |------------+-----------------------------------------------------------| | 12.3XW | Vulnerable; migrate to 12.3(14)YX2 or later | |------------+-----------------------------------------------------------| | 12.3XX | Vulnerable; migrate to 12.4(8) or later | |------------+-----------------------------------------------------------| | 12.3XY | Vulnerable; migrate to 12.4(8) or later | |------------+-----------------------------------------------------------| | 12.3YA | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.3YD | Vulnerable; migrate to 12.4(2)T5 or later | |------------+-----------------------------------------------------------| | 12.3YF | Vulnerable; migrate to 12.3(14)YX2 or later | |------------+-----------------------------------------------------------| | 12.3YG | Vulnerable; migrate to 12.4(2)T5 or later | |------------+-----------------------------------------------------------| | 12.3YH | Vulnerable; migrate to 12.4(2)T5 or later | |------------+-----------------------------------------------------------| | 12.3YI | Vulnerable; migrate to 12.4(2)T5 or later | |------------+-----------------------------------------------------------| | 12.3YJ | Vulnerable; migrate to 12.3(14)YQ8 or later | |------------+-----------------------------------------------------------| | 12.3YK | Vulnerable; migrate to 12.4(4)T4 or later | |------------+-----------------------------------------------------------| | 12.3YM | 12.3(14)YM8 | | |------------+----------------------------+------------------------------| | 12.3YQ | 12.3(14)YQ8 | | |------------+-----------------------------------------------------------| | 12.3YS | Vulnerable; migrate to 12.4(4)T4 or later | |------------+-----------------------------------------------------------| | 12.3YT | Vulnerable; migrate to 12.4(4)T4 or later | |------------+-----------------------------------------------------------| | 12.3YU | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.3YX | 12.3(14)YX2 | | |------------+----------------------------+------------------------------| | 12.3YZ | 12.3(11)YZ1 | | |------------+----------------------------+------------------------------| | Affected | | | | 12.4-Based | Rebuild | Maintenance | | Release | | | |------------+----------------------------+------------------------------| | | 12.4(3e) | | |12.4 |----------------------------+------------------------------| | | 12.4(7b) | 12.4(8) | |------------+----------------------------+------------------------------| | 12.4MR | 12.4(6)MR1 | | |------------+-----------------------------------------------------------| | 12.4SW | All 12.4SW releases are fixed | |------------+-----------------------------------------------------------| | | 12.4(2)T5 | | | |----------------------------+------------------------------| | 12.4T | 12.4(4)T4 | | | |----------------------------+------------------------------| | | 12.4(6)T3 | 12.4(9)T | |------------+-----------------------------------------------------------| | 12.4XA | Vulnerable; migrate to 12.4(6)T3 | |------------+-----------------------------------------------------------| | 12.4XB | Vulnerable; contact TAC | |------------+-----------------------------------------------------------| | 12.4XC | 12.4(4)XC3 | | |------------+----------------------------+------------------------------| | 12.4XD | 12.4(4)XD4 | | |------------+-----------------------------------------------------------| | 12.4XE | All 12.4XE releases are fixed | |------------+-----------------------------------------------------------| | 12.4XG | All 12.4XG releases are fixed | |------------+-----------------------------------------------------------| | 12.4XJ | All 12.4XJ releases are fixed | |------------+-----------------------------------------------------------| | 12.4XP | All 12.4XP releases are fixed | |------------+-----------------------------------------------------------| | 12.4XT | All 12.4XT releases are fixed | +------------------------------------------------------------------------+

Workarounds ===========

Additional mitigations that can be deployed on Cisco devices within the network are available in the Cisco Applied Intelligence companion document for this advisory:

http://www.cisco.com/warp/public/707/cisco-air-20070124-crafted-tcp.shtml

Note: Configuring VTY access-class filters is not an effective mitigation strategy for this vulnerability.

Infrastructure ACLs (iACL) +-------------------------

Although it is often difficult to block traffic transiting your network, it is possible to identify traffic which should never be allowed to target your infrastructure devices and block that traffic at the border of your network. Infrastructure ACLs are considered a network security best practice and should be considered as a long-term addition to good network security as well as a workaround for this specific vulnerability. The ACL example shown below should be included as part of the deployed infrastructure access-list which will protect all devices with IP addresses in the infrastructure IP address range.

A sample access list for devices running Cisco IOS is below:

!--- Permit TCP services from trust hosts destined !--- to infrastructure addresses.

access-list 150 permit tcp TRUSTED_HOSTS MASK INFRASTRUCTURE_ADDRESSES MASK

!--- Deny TCP packets from all other sources destined to infrastructure addresses.

access-list 150 deny tcp any INFRASTRUCTURE_ADDRESSES MASK

!--- Permit all other traffic to transit the device.

access-list 150 permit IP any any

interface serial 2/0 ip access-group 150 in

The white paper entitled "Protecting Your Core: Infrastructure Protection Access Control Lists" presents guidelines and recommended deployment techniques for infrastructure protection access lists. This white paper can be obtained here: http://www.cisco.com/warp/public/707/iacl.html

Receive ACLs (rACL) +------------------

For distributed platforms, Receive ACLs may be an option starting in Cisco IOS Software Versions 12.0(21)S2 for the 12000 (GSR), 12.0(24)S for the 7500, and 12.0(31)S for the 10720. The Receive ACL protects the device from harmful traffic before the traffic can impact the route processor. Receive ACLs are designed to only protect the device on which it is configured. On the 12000, transit traffic is never affected by a receive ACL. Because of this, the destination IP address "any" used in the example ACL entries below only refer to the router's own physical or virtual IP addresses. On the 7500 and 10720, transit traffic with IP options set will be subject to the Receive ACL and permitted or denied accordingly. Receive ACLs are considered a network security best practice, and should be considered as a long-term addition to good network security, as well as a workaround for this specific vulnerability. The white paper entitled "GSR: Receive Access Control Lists" will help you identify and allow legitimate traffic to your device and deny all unwanted packets: http://www.cisco.com/warp/public/707/racl.html

The following is the receive path ACL written to permit this type of traffic from trusted hosts:

!--- Permit tcp services from trusted hosts allowed to the RP.

access-list 151 permit tcp TRUSTED_ADDRESSES MASK any

!--- Deny tcp services from all other sources to the RP.

access-list 151 deny tcp any any

!--- Permit all other traffic to the RP.

access-list 151 permit ip any any

!--- Apply this access list to the 'receive' path.

ip receive access-list 151

Control Plane Policing (CoPP) +----------------------------

The Control Plane Policing (CoPP) feature may be used to mitigate this vulnerability. In the following example, only TCP traffic from trusted hosts and with 'receive' destination IP addresses is permitted to reach the route processor (RP). All other 'transit' IP traffic is unaffected.

It should be noted that dropping traffic from unknown or untrusted IP addresses may affect hosts with dynamically assigned IP addresses from connecting to the Cisco IOS device.

access-list 152 deny tcp TRUSTED_ADDRESSES MASK any access-list 152 permit tcp any any access-list 152 deny ip any any ! class-map match-all permit-tcp-class match access-group 152 ! ! policy-map permit-tcp-policy class permit-tcp-class drop ! control-plane service-policy input permit-tcp-policy

In the above CoPP example, the ACL entries that match the exploit packets with the "permit" action result in these packets being discarded by the policy-map "drop" function, while packets that match the "deny" action are not affected by the policy-map drop function.

Please note that in the 12.2S and 12.0S Cisco IOS trains the policy-map syntax is different:

policy-map permit-tcp-policy class class permit-tcp-class police 32000 1500 1500 conform-action drop exceed-action drop

CoPP is available in Cisco IOS release trains 12.0S, 12.2SX, 12.2S, 12.3T, 12.4, and 12.4T.

Additional information on the configuration and use of the CoPP feature can be found at the following URL:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1838/products_white_paper0...

Anti-spoofing +------------

The Unicast Reverse Path Forwarding (Unicast RPF or uRPF) feature helps to mitigate problems that are caused by spoofed IP source addresses. It is available on Cisco routers and firewalls. For further details, please refer to:

http://www.cisco.com/en/US/partner/products/ps6441/products_command_referenc...

By enabling Unicast Reverse Path Forwarding (uRPF), all spoofed packets will be dropped at the first device. To enable uRPF, use the following commands.

router(config)# ip cef router(config)# interface interface # router(config-if)# ip verify unicast source reachable-via rx

BGP and BTSH/GTSM +----------------

Depending on your release of software, it may be possible to protect your BGP sessions from this memory leak. With the introduction of CSCee73956, Cisco IOS has improved support for BTSH (BGP TTL Security Hack) to reduce, if not eliminate a risk of a memory leak due to this vulnerability. This functionality is also known as GTSM (Generalized TTL Security Mechanism) and documented in RFC 3682. This section refers to GTSM as applied to eBGP sessions only.

Releases of Cisco IOS that contain CSCee73956 are protected from this attack against the BGP port (TCP port 179) only. Other ports should be protected accordingly.

BTSH is not supported for iBGP sessions. BTSH was first introduced in Cisco IOS in 12.0(27)S, 12.3(7)T and 12.2(25)S. Note that the BTSH feature prior to CSCee73956 will not protect against this vulnerability.

For more information on BTSH, please see: http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123newft/123...

Obtaining Fixed Software ========================

Cisco will make free software available to address this vulnerability for affected customers. This advisory will be updated as fixed software becomes available. Prior to deploying software, customers should consult their maintenance provider or check the software for feature set compatibility and known issues specific to their environment.

Customers may only install and expect support for the feature sets they have purchased. By installing, downloading, accessing or otherwise using such software upgrades, customers agree to be bound by the terms of Cisco's software license terms found at http://www.cisco.com/public/sw-license-agreement.html, or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

Do not contact either "psirt@cisco.com" or "security-alert@cisco.com" for software upgrades.

Customers with Service Contracts +-------------------------------

Customers with contracts should obtain upgraded software through their regular update channels. For most customers, this means that upgrades should be obtained through the Software Center on Cisco's worldwide website at http://www.cisco.com.

Customers using Third Party Support Organizations +------------------------------------------------

Customers whose Cisco products are provided or maintained through prior or existing agreement with third-party support organizations such as Cisco Partners, authorized resellers, or service providers should contact that support organization for guidance and assistance with the appropriate course of action in regards to this advisory.

The effectiveness of any workaround or fix is dependent on specific customer situations such as product mix, network topology, traffic behavior, and organizational mission. Due to the variety of affected products and releases, customers should consult with their service provider or support organization to ensure any applied workaround or fix is the most appropriate for use in the intended network before it is deployed.

Customers without Service Contracts +----------------------------------

Customers who purchase direct from Cisco but who do not hold a Cisco service contract and customers who purchase through third-party vendors but are unsuccessful at obtaining fixed software through their point of sale should get their upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC contacts are as follows.

* +1 800 553 2447 (toll free from within North America) * +1 408 526 7209 (toll call from anywhere in the world) * e-mail: tac@cisco.com

Have your product serial number available and give the URL of this notice as evidence of your entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC.

Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for additional TAC contact information, including special localized telephone numbers and instructions and e-mail addresses for use in various languages.

Exploitation and Public Announcements =====================================

The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.

This vulnerability was discovered by Cisco during our internal testing process.

Status of this Notice: FINAL ============================

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.

A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.

Distribution ============

This advisory is posted on Cisco's worldwide website at: http://www.cisco.com/warp/public/707/cisco-sa-20070124-crafted-tcp.shtml

In addition to worldwide web posting, a text version of this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail and Usenet news recipients.

* cust-security-announce@cisco.com * first-teams@first.org * bugtraq@securityfocus.com * vulnwatch@vulnwatch.org * cisco@spot.colorado.edu * cisco-nsp@puck.nether.net * full-disclosure@lists.grok.org.uk * comp.dcom.sys.cisco@newsgate.cisco.com

Future updates of this advisory, if any, will be placed on Cisco's worldwide website, but may or may not be actively announced on mailing lists or newsgroups. Users concerned about this problem are encouraged to check the above URL for any updates.

Revision History ================

+---------------------------------------+ | | | Initial | | 1.0 | 2007-January-24 | public | | | | release. | +---------------------------------------+

Cisco Security Procedures =========================

Complete information on reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco, is available on Cisco's worldwide website at http://www.cisco.com/en/US/products/products_security_vulnerability_policy.h... This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at http://www.cisco.com/go/psirt

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