[apops] Cisco Security Advisory: Cisco IOS XR Software Border Gateway Pr

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  • Subject: [apops] Cisco Security Advisory: Cisco IOS XR Software Border Gateway Protocol Vulnerability
  • From: Cisco Systems Product Security Incident Response Team <psirt at cisco dot com>
  • Date: Fri, 27 Aug 2010 20:00:00 -0400
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      Cisco Security Advisory: Cisco IOS XR Software Border Gateway
      Protocol Vulnerability
      
      Advisory ID: cisco-sa-20100827-bgp
      
      Revision 1.0
      
      For Public Release 2010 August 27 2200 UTC (GMT)
      
      +---------------------------------------------------------------------
      
      Summary
      =======
      
      Cisco IOS XR Software contains a vulnerability in the Border Gateway
      Protocol (BGP) feature. The vulnerability manifests itself when a BGP
      peer announces a prefix with a specific, valid but unrecognized
      transitive attribute. On receipt of this prefix, the Cisco IOS XR
      device will corrupt the attribute before sending it to the
      neighboring devices. Neighboring devices that receive this corrupted
      update may reset the BGP peering session.
      
      Affected devices running Cisco IOS XR Software corrupt the
      unrecognized attribute before sending to neighboring devices, but
      neighboring devices may be running operating systems other than Cisco
      IOS XR Software and may still reset the BGP peering session after
      receiving the corrupted update. This is per standards defining the
      operation of BGP.
      
      Cisco developed a fix that addresses this vulnerability and will be
      releasing free software maintenance upgrades (SMU) progressively
      starting 28 August 2010. This advisory will be updated accordingly as
      fixes become available.
      
      This advisory is posted at:
      
      http://www.cisco.com/warp/public/707/cisco-sa-20100827-bgp.shtml
      
      Affected Products
      =================
      
      This vulnerability affects all Cisco IOS XR Software devices
      configured with BGP routing.
      
      Vulnerable Products
      +------------------
      
      To determine the Cisco IOS XR Software release that is running on a
      Cisco product, administrators can log in to the device and issue the 
      "show version" command to display the system banner. The system banner
      confirms that the device is running Cisco IOS XR Software by
      displaying text similar to "Cisco IOS XR Software". The software
      version is displayed after the text "Cisco IOS XR Software".
      
      The following example identifies a Cisco CRS-1 that is running Cisco
      IOS XR Software Release 3.6.2:
      
          RP/0/RP0/CPU0:CRS#show version
          Tue Aug 18 14:25:17.407 AEST
          
          Cisco IOS XR Software, Version 3.6.2[00]
          Copyright (c) 2008 by Cisco Systems, Inc.
          
          ROM: System Bootstrap, Version 1.49(20080319:195807) [CRS-1 ROMMON],
          
          CRS uptime is 4 weeks, 4 days, 1 minute
          System image file is "disk0:hfr-os-mbi-3.6.2/mbihfr-rp.vm"
          
          cisco CRS-8/S (7457) processor with 4194304K bytes of memory.
          7457 processor at 1197Mhz, Revision 1.2
          
          17 Packet over SONET/SDH network interface(s)
          1 DWDM controller(s)
          17 SONET/SDH Port controller(s)
          8 TenGigabitEthernet/IEEE 802.3 interface(s)
          2 Ethernet/IEEE 802.3 interface(s)
          1019k bytes of non-volatile configuration memory.
          38079M bytes of hard disk.
          981440k bytes of ATA PCMCIA card at disk 0 (Sector size 512 bytes).
          
          Configuration register on node 0/0/CPU0 is 0x102
          Boot device on node 0/0/CPU0 is mem:
          
          
          !--- output truncated
      
      The following example identifies a Cisco 12404 router that is running
      Cisco IOS XR Software Release 3.7.1:
      
          RP/0/0/CPU0:GSR#show version
          
          Cisco IOS XR Software, Version 3.7.1[00]
          Copyright (c) 2008 by Cisco Systems, Inc.
          
          ROM: System Bootstrap, Version 12.0(20051020:160303) SOFTWARE
          Copyright (c) 1994-2005 by cisco Systems,  Inc.
          
          GSR uptime is 3 weeks, 6 days, 3 hours, 20 minutes
          System image file is "disk0:c12k-os-mbi-3.7.1/mbiprp-rp.vm"
          
          cisco 12404/PRP (7457) processor with 2097152K bytes of memory.
          7457 processor at 1266Mhz, Revision 1.2
          
          1 Cisco 12000 Series Performance Route Processor
          1 Cisco 12000 Series - Multi-Service Blade Controller
          1 1 Port ISE Packet Over SONET OC-48c/STM-16 Controller (1 POS)
          1 Cisco 12000 Series SPA Interface Processor-601/501/401
          3 Ethernet/IEEE 802.3 interface(s)
          1 SONET/SDH Port controller(s)
          1 Packet over SONET/SDH network interface(s)
          4 PLIM QoS controller(s)
          8 FastEthernet/IEEE 802.3 interface(s)
          1016k bytes of non-volatile configuration memory.
          1000496k bytes of disk0: (Sector size 512 bytes).
          65536k bytes of Flash internal SIMM (Sector size 256k).
          
          Configuration register on node 0/0/CPU0 is 0x2102
          Boot device on node 0/0/CPU0 is disk0:
          
          
          !--- output truncated
      
      Additional information about Cisco IOS XR Software release naming
      conventions is available in the "White Paper: Cisco IOS Reference
      Guide" at the following link:
      
      http://www.cisco.com/web/about/security/intelligence/ios-ref.html#9
      
      Additional information about Cisco IOS XR Software time-based release
      model is available in the "White Paper: Guidelines for Cisco IOS XR
      Software" at the following link:
      
      http://www.cisco.com/en/US/prod/collateral/iosswrel/ps8803/ps5845/product_bulletin_c25-478699.html
      
      BGP is configured in Cisco IOS XR Software with the configuration
      command "router bgp [AS Number]" or "router bgp [X.Y]". The device is
      vulnerable if it is running an affected Cisco IOS XR Software version
      and has BGP configured.
      
      The following example shows a Cisco IOS XR Software device configured
      with BGP:
      
          RP/0/0/CPU0:GSR#show running-config | begin router bgp
          Building configuration...
          router bgp 65535
           bgp router-id 192.168.0.1
           address-family ipv4 unicast
            network 192.168.1.1/32
           !
           address-family vpnv4 unicast
           !
           neighbor 192.168.2.1
            remote-as 65534
            update-source Loopback0
            address-family ipv4 unicast
            !
          
          
          !--- output truncated
      
      Products Confirmed Not Vulnerable
      +--------------------------------
      
      The following Cisco products are confirmed not vulnerable:
      
        * Cisco IOS Software
        * Cisco IOS XR Software not configured for BGP routing
      
      No other Cisco products are currently known to be affected by these
      vulnerabilities.
      
      Details
      =======
      
      This vulnerability affects Cisco IOS XR devices running affected
      software versions and configured with the BGP routing feature.
      
      The vulnerability manifests itself when a BGP peer announces a prefix
      with a specific, valid but unrecognized transitive attribute. On
      receipt of this prefix, the Cisco IOS XR device will corrupt the
      attribute before sending it to the neighboring devices. Neighboring
      devices that receive this corrupted update may reset the BGP peering
      session.
      
      Affected devices running Cisco IOS XR Software corrupt the
      unrecognized attribute before sending to neighboring devices, but
      neighboring devices may be running operating systems other than Cisco
      IOS XR Software and may still reset the BGP peering session after
      receiving the corrupted update. This is per RFC 4271 that defines the
      operation of BGP.
      
      After an affected device running Cisco IOS XR Software sends a
      corrupted update, it will receive a notification from the neighboring
      router and will create a log message like the following example:
      
          bgp[122]: %ROUTING-BGP-5-ADJCHANGE : neighbor 172.16.1.251 Down - BGP Notification received: update malformed
      
      This vulnerability is documented in Cisco Bug ID CSCti62211 and has
      been assigned Common Vulnerabilities and Exposures (CVE) ID
      CVE-2010-3035.
      
      Vulnerability Scoring Details
      =============================
      
      Cisco has provided scores for the vulnerabilities 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
      
      CSCti62211 - BGP flaps due to unknown attribute
      
      CVSS Base Score - 5
      
      Access Vector           - Network
      Access Complexity       - Low
      Authentication          - None
      Confidentiality Impact  - None
      Integrity Impact        - None
      Availability Impact     - Partial
      
      CVSS Temporal Score - 4.8
      
      Exploitability          - Functional
      Remediation Level       - Unavailable
      Report Confidence       - Confirmed
      
      Impact
      ======
      
      Successful exploitation of these vulnerabilities may result in the
      continuous resetting of BGP peering sessions. This may lead to
      routing inconsistencies and a denial of service for those affected
      networks.
      
      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.
      
      +-------------------------------------------------------------------+
      | Cisco IOS XR  |            SMU ID            |  SMU  |  Requires  |
      |    Version    |                              | Name  |   Reload   |
      |---------------+------------------------------+-------+------------|
      | 3.4.0         | Vulnerable; Migrate to 3.4.3 |       |            |
      |               | and apply a SMU              |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.4.1         | SMU will be available on     |       |            |
      |               | 2010-Sep-9                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.4.2         | SMU will be available on     |       |            |
      |               | 2010-Sep-9                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.4.3         | SMU will be available on     |       |            |
      |               | 2010-Sep-5                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.5.2         | SMU will be available on     |       |            |
      |               | 2010-Sep-5                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.5.3         | SMU will be available on     |       |            |
      |               | 2010-Sep-9                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.5.4         | SMU will be available on     |       |            |
      |               | 2010-Sep-5                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.6.0         | SMU will be available on     |       |            |
      |               | 2010-Sep-9                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.6.1         | SMU will be available on     |       |            |
      |               | 2010-Sep-3                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.6.2         | SMU will be available on     |       |            |
      |               | 2010-Aug-30                  |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.6.3         | SMU will be available on     |       |            |
      |               | 2010-Sep-3                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.7.0         | SMU will be available on     |       |            |
      |               | 2010-Sep-9                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.7.1         | SMU will be available on     |       |            |
      |               | 2010-Sep-1                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.7.2         | SMU will be available on     |       |            |
      |               | 2010-Sep-3                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.7.3         | SMU will be available on     |       |            |
      |               | 2010-Sep-3                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.8.0         | SMU will be available on     |       |            |
      |               | 2010-Sep-3                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.8.1         | SMU will be available on     |       |            |
      |               | 2010-Sep-3                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.8.2         | SMU will be available on     |       |            |
      |               | 2010-Aug-30                  |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.8.3         | SMU will be available on     |       |            |
      |               | 2010-Sep-1                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.8.4         | SMU will be available on     |       |            |
      |               | 2010-Aug-28                  |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.9.0         | SMU will be available on     |       |            |
      |               | 2010-Sep-1                   |       |            |
      |---------------+------------------------------+-------+------------|
      | 3.9.1         | SMU will be available on     |       |            |
      |               | 2010-Aug-28                  |       |            |
      +-------------------------------------------------------------------+
      
      Workarounds
      ===========
      
      There are no workarounds to proactively mitigate this vulnerability.
      If a route flap is observed, the prefix with the unrecognized
      attribute can be filtered. For further information on filtering on
      Cisco IOS XR Software, please consult the document "Implementing
      Routing Policy on Cisco IOS XR Software" at the following link:
      
      http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.0/routing/configuration/guide/rc3rpl.html#wp1118699
      
      Obtaining Fixed Software
      ========================
      
      Cisco is releasing free software updates that address these
      vulnerabilities. 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
      =====================================
      
      An advertisement of an unrecognized but valid BGP attribute resulted
      in resetting of several BGP neighbors on 27 August 2010. This
      advertisement was not malicious but inadvertently triggered this
      vulnerability.
      
      The Cisco PSIRT is not aware of malicious use of the vulnerability
      described in this advisory.
      
      Status of this Notice: INTERIM
      ==============================
      
      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. CISCO EXPECTS TO UPDATE THIS DOCUMENT AS NEW
      INFORMATION BECOMES AVAILABLE.
      
      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-20100827-bgp.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      | 2010-August-27 | 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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