[apops] Cisco Security Advisory: Cisco IOS cTCP Denial of Service Vulner

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  • Subject: [apops] Cisco Security Advisory: Cisco IOS cTCP Denial of Service Vulnerability
  • From: Cisco Systems Product Security Incident Response Team <psirt at cisco dot com>
  • Date: Wed, 25 Mar 2009 17:00:00 +0100
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      Cisco Security Advisory: Cisco IOS cTCP Denial of Service
      Vulnerability
      
      Advisory ID: cisco-sa-20090325-ctcp
      
      http://www.cisco.com/warp/public/707/cisco-sa-20090325-ctcp.shtml
      
      Revision 1.0
      
      For Public Release 2009 March 25 1600 UTC (GMT)
      
      - ---------------------------------------------------------------------
      
      Summary
      =======
      
      A series of TCP packets may cause a denial of service (DoS) condition
      on Cisco IOS devices that are configured as Easy VPN servers with the
      Cisco Tunneling Control Protocol (cTCP) encapsulation feature. Cisco
      has released free software updates that address this vulnerability.
      No workarounds are available; however, the IPSec NAT traversal
      (NAT-T) feature can be used as an alternative.
      
      This advisory is posted at 
      http://www.cisco.com/warp/public/707/cisco-sa-20090325-ctcp.shtml
      
      Note: The March 25, 2009, Cisco IOS Security Advisory bundled
      publication includes eight Security Advisories. All of the advisories
      address vulnerabilities in Cisco IOS Software. Each advisory lists
      the releases that correct the vulnerability or vulnerabilities in the
      advisory. The following table lists releases that correct all Cisco
      IOS Software vulnerabilities that have been published in Cisco
      Security Advisories on March 25, 2009, or earlier.
      
      http://www.cisco.com/warp/public/707/cisco-sa-20090325-bundle.shtml
      
      Individual publication links are listed below:
      
        * Cisco IOS cTCP Denial of Service Vulnerability
          http://www.cisco.com/warp/public/707/cisco-sa-20090325-ctcp.shtml
      
        * Cisco IOS Software Multiple Features IP Sockets Vulnerability
          http://www.cisco.com/warp/public/707/cisco-sa-20090325-ip.shtml
      
        * Cisco IOS Software Mobile IP and Mobile IPv6 Vulnerabilities
          http://www.cisco.com/warp/public/707/cisco-sa-20090325-mobileip.shtml
      
        * Cisco IOS Software Secure Copy Privilege Escalation Vulnerability
          http://www.cisco.com/warp/public/707/cisco-sa-20090325-scp.shtml
      
        * Cisco IOS Software Session Initiation Protocol Denial of Service
          Vulnerability
          http://www.cisco.com/warp/public/707/cisco-sa-20090325-sip.shtml
      
        * Cisco IOS Software Multiple Features Crafted TCP Sequence
          Vulnerability
          http://www.cisco.com/warp/public/707/cisco-sa-20090325-tcp.shtml
      
        * Cisco IOS Software Multiple Features Crafted UDP Packet
          Vulnerability
          http://www.cisco.com/warp/public/707/cisco-sa-20090325-udp.shtml
      
        * Cisco IOS Software WebVPN and SSLVPN Vulnerabilities
          http://www.cisco.com/warp/public/707/cisco-sa-20090325-webvpn.shtml
      
      Affected Products
      =================
      
      Vulnerable Products
      +------------------
      
      Cisco IOS devices running versions 12.4(9)T or later and configured
      for Cisco Tunneling Control Protocol (cTCP) encapsulation for EZVPN
      server are vulnerable.
      
      Note: The cTCP encapsulation feature was introduced in Cisco IOS
      version 12.4(9)T. The cTCP encapsulation feature is disabled by
      default. Cisco IOS devices configured for EZVPN client are not
      affected by this vulnerability. Only devices configured as EZVPN
      servers are vulnerable.
      
      To configure the cTCP encapsulation feature for Easy VPN, use the
      crypto ctcp command in global configuration mode. You can optionally
      specify the port number that the device will listen to with the
      crypto ctcp port <port> command. Up to ten numbers can be configured
      and the port value can be from 1 through 65535. If the port keyword
      is not configured, the default port number is 10000. In the following
      example, the Cisco IOS device is configured to listen for cTCP
      messages on port 10000.
      
          crypto ctcp port 10000
      
      Note: The port keyword is configured only on the Cisco IOS device
      acting as an EZVPN server.
      
      To determine the version of the Cisco IOS 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
      Software release 12.3(26) with an installed image name of C2500-IS-L:
      
              Router#show version
              Cisco Internetwork Operating System Software
              IOS (tm) 2500 Software (C2500-IS-L), Version 12.3(26), RELEASE SOFTWARE (fc2)
              Technical Support: http://www.cisco.com/techsupport
              Copyright (c) 1986-2008 by cisco Systems, Inc.
              Compiled Mon 17-Mar-08 14:39 by dchih
      
            <output truncated>
      
      
      The next example shows a product running Cisco IOS Software release
      12.4(20)T with an image name of C1841-ADVENTERPRISEK9-M:
      
              Router#show version
              Cisco IOS Software, 1841 Software (C1841-ADVENTERPRISEK9-M), Version 12.4(20)T, RELEASE SOFTWARE (fc3)
              Technical Support: http://www.cisco.com/techsupport
              Copyright (c) 1986-2008 by Cisco Systems, Inc.
              Compiled Thu 10-Jul-08 20:25 by prod_rel_team
      
            <output truncated>
      
      Additional information on the Cisco IOS release naming conventions
      can be found on the document entitled "White Paper: Cisco IOS
      Reference Guide", which is available at 
      http://www.cisco.com/warp/public/620/1.html
      
      Products Confirmed Not Vulnerable
      +--------------------------------
      
      Cisco IOS devices that are not configured for cTCP are not affected
      by this vulnerability. The Cisco ASA and Cisco VPN 3000 series
      concentrators are not vulnerable. Cisco IOS devices configured as
      EZVPN clients are not affected by this vulnerability. The Cisco VPN
      Client is not vulnerable. Cisco IOS-XR and Cisco IOS-XE software are
      not affected by this vulnerability. No other Cisco products are
      currently known to be affected by this vulnerability.
      
      Details
      =======
      
      The Cisco Tunneling Control Protocol (cTCP) feature is used by Easy
      VPN remote device operating in an environment in which standard IPSec
      does not function transparently without modification to existing
      firewall rules. The cTCP traffic is actually TCP traffic. Cisco IOS
      cTCP packets are Internet Key Exchange (IKE) or Encapsulating
      Security Payload (ESP) packets that are being transmitted over TCP.
      
      A vulnerability exists where a series of TCP packets may cause a
      Cisco IOS device that is configured as an Easy VPN server with the
      cTCP encapsulation feature to run out of memory. This vulnerability
      is documented in Cisco Bug IDs CSCsr16693 and CSCsu21828; and has 
      been assigned the Common Vulnerabilities and Exposures (CVE) 
      identifier CVE-2009-0635.
      
      Vulnerability Scoring Details
      =============================
      
      Cisco has provided scores for the vulnerability in this advisory
      based on the Common Vulnerability Scoring System (CVSS). The CVSS
      scoring in this Security Advisory is done in accordance with CVSS
      version 2.0.
      
      CVSS is a standards-based scoring method that conveys vulnerability
      severity and helps determine urgency and priority of response.
      
      Cisco has provided a base and temporal score. Customers can then
      compute environmental scores to assist in determining the impact of
      the vulnerability in individual networks.
      
      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 at
      
      http://intellishield.cisco.com/security/alertmanager/cvss.
      
      CSCsr16693 - cTCP server may crash when processing a series of TCP
                   packets
      
      CVSS Base Score - 7.8
      
       Access Vector           - Network
       Access Complexity       - Low
       Authentication          - None
       Confidentiality Impact  - None
       Integrity Impact        - None
       Availability Impact     - Complete
      
      CVSS Temporal Score - 6.4
      
       Exploitability          - Functional
       Remediation Level       - Official-Fix
       Report Confidence       - Confirmed
      
      CSCsu21828 - Cisco IOS Device may crash with cTCP enabled
      
      CVSS Base Score - 7.8
      
       Access Vector           - Network
       Access Complexity       - Low
       Authentication          - None
       Confidentiality Impact  - None
       Integrity Impact        - None
       Availability Impact     - Complete
      
      CVSS Temporal Score - 6.4
      
       Exploitability          - Functional
       Remediation Level       - Official-Fix
       Report Confidence       - Confirmed
      
      Impact
      ======
      
      Successful exploitation of this vulnerability may cause the affected
      device to run out of memory. Repeated exploitation will result in a
      denial of service (DoS) condition.
      
      Software Versions 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) names a Cisco IOS
      release train. If a given release train is vulnerable, then the
      earliest possible releases that contain the fix (along with the
      anticipated date of availability for each, if applicable) are listed
      in the "First Fixed Release" column of the table. The "Recommended
      Release" column indicates the releases which have fixes for all the
      published vulnerabilities at the time of this Advisory. 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. Cisco recommends upgrading to a release equal to or
      later than the release in the "Recommended Releases" column of the
      table.
      
      +-------------------------------------------------------------------+
      |   Major Release   |       Availability of Repaired Releases       |
      |-------------------+-----------------------------------------------|
      | Affected          |                       |                       |
      | 12.0-Based        | First Fixed Release   | Recommended Release   |
      | Releases          |                       |                       |
      |-------------------------------------------------------------------|
      | There are no affected 12.0 based releases                         |
      |-------------------------------------------------------------------|
      | Affected          |                       |                       |
      | 12.1-Based        | First Fixed Release   | Recommended Release   |
      | Releases          |                       |                       |
      |-------------------------------------------------------------------|
      | There are no affected 12.1 based releases                         |
      |-------------------------------------------------------------------|
      | Affected          |                       |                       |
      | 12.2-Based        | First Fixed Release   | Recommended Release   |
      | Releases          |                       |                       |
      |-------------------------------------------------------------------|
      | There are no affected 12.2 based releases                         |
      |-------------------------------------------------------------------|
      | Affected          |                       |                       |
      | 12.3-Based        | First Fixed Release   | Recommended Release   |
      | Releases          |                       |                       |
      |-------------------------------------------------------------------|
      | There are no affected 12.3 based releases                         |
      |-------------------------------------------------------------------|
      | Affected          |                       |                       |
      | 12.4-Based        | First Fixed Release   | Recommended Release   |
      | Releases          |                       |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4              | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4JA            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4JDA           | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4JK            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4JL            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4JMA           | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4JMB           | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4JX            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4MD            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4MR            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4SW            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      |                   | 12.4(20)T2            | 12.4(22)T1            |
      | 12.4T             |                       |                       |
      |                   | 12.4(15)T9; Available | 12.4(15)T9; Available |
      |                   | on 29-APR-2009        | on 29-APR-2009        |
      |-------------------+-----------------------+-----------------------|
      | 12.4XA            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XB            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XC            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XD            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XE            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XF            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XG            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XJ            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XK            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XL            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XM            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XN            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XP            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XQ            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XR            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XT            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XV            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XW            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XY            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4XZ            | 12.4(15)XZ2           | 12.4(15)XZ2           |
      |-------------------+-----------------------+-----------------------|
      | 12.4YA            | 12.4(20)YA2           | 12.4(20)YA3           |
      |-------------------+-----------------------+-----------------------|
      | 12.4YB            | Not Vulnerable        |                       |
      |-------------------+-----------------------+-----------------------|
      | 12.4YD            | Not Vulnerable        |                       |
      +-------------------------------------------------------------------+
      
      Workarounds
      ===========
      
      No workarounds are available.
      
      As an alternative, the IPSec NAT traversal (NAT-T) feature can be
      used. The IPSec NAT-T feature introduces support for IP Security
      (IPSec) traffic to travel through Network Address Translation (NAT)
      or Port Address Translation (PAT) points in the network by addressing
      many known incompatabilites between NAT and IPSec.
      
      Note: The NAT-T feature was introduced in Cisco IOS version 12.2(13)
      T.
      
      NAT Traversal is a feature that is auto detected by VPN devices.
      There are no configuration steps for a router running Cisco IOS
      Release 12.2(13)T and later. If both VPN devices are NAT-T capable,
      NAT Traversal is auto-detected and auto-negotiated.
      
      Note: When you enable NAT-T, the Cisco IOS device automatically opens
      UDP port 4500 on all IPSec enabled interfaces.
      
      Caution: Be aware that you may need to enable IPSec over UDP on Cisco
      VPN software clients to support NAT-T. Additionally, you may need to
      change firewall rules to allow UDP port 500 for Internet Key Exchange
      (IKE) and UDP port 4500 for NAT-T.
      
      For more information about NAT-T, refer to the white paper at:
      
      http://www.cisco.com/en/US/docs/ios/security/configuration/guide/sec_ipsec_nat_transp.html
      
      Additional mitigations that can be deployed on Cisco devices within
      the network are available in the Cisco Applied Mitigation Bulletin
      companion document for this advisory, which is available at the
      following link:
      
      http://www.cisco.com/warp/public/707/cisco-amb-20090325-ctcp.shtml
      
      Obtaining Fixed Software
      ========================
      
      Cisco has released free software updates that address this
      vulnerability. 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/en/US/docs/general/warranty/English/EU1KEN_.html
      or as otherwise set forth at Cisco.com Downloads at 
      http://www.cisco.com/public/sw-center/sw-usingswc.shtml
      
      Do not contact psirt at cisco dot com or security-alert at cisco dot 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 agreements 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 do not hold a Cisco
      service contract, and customers who purchase through third-party
      vendors but are unsuccessful in obtaining fixed software through
      their point of sale should acquire 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 at cisco dot com
      
      Customers should have their product serial number available and be
      prepared to give the URL of this notice as evidence of entitlement to
      a free upgrade. Free upgrades for non-contract customers must be
      requested through the TAC.
      
      Refer to http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html
      for additional TAC contact information, including 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 found during the resolution of a technical
      support service request.
      
      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-20090325-ctcp.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 at cisco dot com
        * first-bulletins at lists dot first dot org
        * bugtraq at securityfocus dot com
        * vulnwatch at vulnwatch dot org
        * cisco at spot dot colorado dot edu
        * cisco-nsp at puck dot nether dot net
        * full-disclosure at lists.grok dot org dot uk
        * comp.dcom.sys.cisco at newsgate dot cisco dot 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
      ================
      
      +---------------------------------------+
      | Revision |               | Initial    |
      | 1.0      | 2009-March-25 | 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.html
      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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