Operating System:

Published:

13 May 2001

Protect yourself against future threats.

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===========================================================================
             AUSCERT External Security Bulletin Redistribution

                  ESB-2001.194 -- Cisco Security Advisory
             Cisco IOS BGP Attribute Corruption Vulnerability
                                14 May 2001

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Vendor:                 Cisco Systems
Operating System:       Cisco IOS
Impact:                 Denial of Service
Access Required:        Remote

- --------------------------BEGIN INCLUDED TEXT--------------------

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Cisco Security Advisory: Cisco IOS BGP Attribute Corruption Vulnerability
=========================================================================
Revision 1.0

For Public Release 2001 May 10 08:00 AM US/Pacific (UTC -0700)

  ------------------------------------------------------------------------

Summary
=======

A Border Gateway Protocol (BGP) UPDATE contains Network Layer
Reachability  Information (NLRI) and attributes that describe the path to
the destination. An unrecognized transitive attribute can cause failures in
Cisco IOS routers, ranging from a crash upon receipt of the unrecognized
transitive attribute, to a later failure upon attempt to clear the
unrecognized transitive attribute. Specific but common configurations are
affected, and described below.  The failure was discovered  because of a
malfunction in the BGP implementation of another vendor. There is no
workaround.  Affected customers are urged to upgrade to fixed code.

This vulnerability has been assigned Cisco bug ID CSCdt79947.

The complete text of this advisory will be located at
http://www.cisco.com/warp/public/707/ios-bgp-attr-corruption-pub.shtml

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

Configurations including  BGP4 Prefix Filtering with Inbound Route Maps are
vulnerable.  BGP with prefix or inbound routemap filtering was introduced
in Cisco IOSĀ® Software version 11.2  The following versions of Cisco IOS
Software are affected and listed in the table below: 11.CC and its
derivatives, 11.2 and its  derivaties, 11.3, 11.3T, 12.0, 12.0S and special
branches taken out of 12.0 are all affected. The versions of Cisco IOS
Software based on 12.1, 12.0(5)T, 12.2, 12.0ST, and 12.1(E) are not
affected. The following products are affected if they run a Cisco IOS
software release that has the defect. To determine if a Cisco product is
running an affected IOS, log in to the device and issue the show version
command. Cisco IOS software will identify itself as "Internetwork Operating
System Software" or "IOS (tm)" software and will display a version number.
Other Cisco devices either will not have the show version command, or will
give different output. Compare the version number obtained from the router
with the versions presented in the Software Versions and Fixes section
below.

Cisco devices that may be running with affected Cisco IOS software releases
include:

   * Cisco routers in the AGS/MGS/CGS/AGS+, IGS, RSM, 800, ubr900, 1000,
     1400, 1500, 1600, 1700, 2500, 2600, 3000, 3600, 3800, 4000, 4500,
     4700, AS5200, AS5300, AS5800, 6400, 7000, 7200, ubr7200, 7500, and
     12000 series.

Cisco devices that may be running Cisco IOS Software, but do NOT support
BGP and are therefore not vulnerable include:

   * Most recent versions of the LS1010 ATM switch.
   * The Catalyst 2900XL LAN switch only if it is running IOS.
   * The Catalyst 1900, 2800, 2900, 3000, and 5000 series LAN switches.
   * The Cisco DistributedDirector.

If you are not running Cisco IOS software, you are not affected by this
vulnerability.  If you are not running BGP, you are not affected by this
vulnerability.

Cisco products that do not run Cisco IOS software and are not affected by
this defect include, but are not limited to:

   * 700 series dialup routers (750, 760, and 770 series) are not affected.
   * The Catalyst 6000 is not affected if it is not running IOS.
   * WAN switching products in the IGX and BPX lines are not affected.
   * The MGX (formerly known as the AXIS shelf) is not affected.
   * No host-based software is affected.
   * The Cisco PIX Firewall is not affected.
   * The Cisco LocalDirector is not affected.
   * The Cisco Cache Engine is not affected.

Details
=======

A Border Gateway Protocol (BGP) UPDATE contains Network Layer Reachability
Information (NLRI) and attributes that describe the path to the
destination. Each path attribute is a type, length, value (TLV) object.
This failure occurs as a result of memory corruption and only in
configurations using specific inbound route filtering. The failure was
discovered because of a malfunction in the BGP implementation of another
vendor. There is no workaround.

Impact
======

The vulnerability can be exercised repeatedly, affecting core routers,
creating widespread network outages. This vulnerability can only be
exercised in configurations that include both BGP and inbound route
filtering on affected software.

Software Versions and Fixes
===========================

The following table summarizes the Cisco IOS software releases that are
known to be affected, and the earliest estimated dates of availability for
the recommended fixed versions. Dates are always tentative and subject to
change.

Each row of the table 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 and the
anticipated date of availability for each are listed in the "Rebuild",
"Interim", and "Maintenance" columns. A device running any release in the
given train that is earlier than the release in a specific column (less
than the earliest fixed release) is known to be vulnerable, and it should
be upgraded at least to the indicated release or a later version (greater
than the earliest fixed release label).

When selecting a release, keep in mind the following definitions:

     Maintenance
          Most heavily tested and highly recommended release of any label
          in a given row of the table.

     Rebuild
          Constructed from the previous maintenance or major release in the
          same train, it contains the fix for a specific defect. Although
          it receives less testing, it contains only the minimal changes
          necessary to effect the repair.

     Interim
          Built at regular intervals between maintenance releases and
          receive less testing. Interims should be selected only if there
          is no other suitable release that addresses the vulnerability,
          and interim images should be upgraded to the next available
          maintenance release as soon as possible. Interim releases are not
          available via manufacturing, and usually they are not available
          for customer download from CCO without prior arrangement with the
          Cisco TAC.

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 TAC for
assistance as shown later in this notice.

More information on Cisco IOS Software release names and abbreviations is
available at
http://www.cisco.com/warp/public/cc/pd/iosw/iore/prodlit/537_pp.htm.


+===========================================================================+
    Train     Description of            Availability of Fixed Releases*
             Image or Platform
+===========================================================================+
      11.0-based Releases           Rebuild         Interim    Maintenance
+===========================================================================+
    11.0     Major GD release   Not vulnerable
             for all platforms
+===========================================================================+
      11.1-based Releases           Rebuild         Interim    Maintenance
+===========================================================================+
    11.1     Major release for Not vulnerable
             all platforms
+----------+------------------+-----------------+------------+--------------+
             ED release for
   11.1AA    access servers:   Not vulnerable
             1600, 3200, and
             5200 series.
+----------+------------------+-----------------+------------+--------------+
             Platform-specific End of Engineering
   11.1CA    support for 7500,
             7200, 7000, and
             RSP               Not scheduled
+----------+------------------+-----------------+------------+--------------+
             ISP train: added
             support for FIB,  11.1(36)CC2
   11.1CC    CEF, and NetFlow
             on 7500, 7200,    Not scheduled
             7000, and RSP
+----------+------------------+-----------------+------------+--------------+
             Added support for End of Engineering
   11.1CT    Tag Switching on
             7500, 7200, 7000,
             and RSP           Upgrade recommended to 12.0(14)ST
+----------+------------------+-----------------+------------+--------------+
   11.1IA    Distributed       Not Vulnerable
             Director only
+===========================================================================+
      11.2-based Releases           Rebuild         Interim    Maintenance
+===========================================================================+
             Major release,     End of Engineering
    11.2     general
             deployment        Not scheduled
+----------+------------------+-----------------+------------+--------------+
             Platform-specific
             support for IBM   End of Engineering
   11.2BC    networking, CIP,
             and TN3270 on
             7500, 7000, and   Upgrade recommended to 12.1(8)
             RSP
+----------+------------------+-----------------+------------+--------------+
                               End of Engineering
    11.2F    Feature train for
             all platforms     Upgrade recommended
+----------+------------------+-----------------+------------+--------------+
             Early deployment  End of Engineering
   11.2GS    release to
             support 12000 GSR Upgrade recommended to 12.0(17)S
+----------+------------------+-----------------+------------+--------------+
                               End of Engineering
    11.2P    New platform
             support           Upgrade recommended to 12.0(17)
+----------+------------------+-----------------+------------+--------------+
   11.2SA    Catalyst 2900XL   Not vulnerable
             switch only
+----------+------------------+-----------------+------------+--------------+
   11.2WA3   LightStream 1010  Not vulnerable
             ATM switch
+----------+------------------+-----------------+------------+--------------+
             Initial release   End of Engineering
 11.2(4)XAf  for the 1600 and
             3600              Upgrade recommended
+----------+------------------+-----------------+------------+--------------+
             Initial release
             for the 5300 and  End of Engineering
  11.2(9)XA  digital modem
             support for the   Upgrade recommended
             3600
+===========================================================================+
      11.3-based Releases           Rebuild         Interim    Maintenance
+===========================================================================+
                               End of Engineering
    11.3     Major release for
             all platforms     Upgrade recommended to 12.0(17)
+----------+------------------+-----------------+------------+--------------+
             ED for dial
             platforms and     End of Engineering
   11.3AA    access servers:
             5800, 5200, 5300, Upgrade recommended to 12.0(17)
             7200
+----------+------------------+-----------------+------------+--------------+
             Early deployment  End of Engineering
   11.3DA    train for ISP
             DSLAM 6200
             platform          Upgrade recommended to 12.1(5)DA1
+----------+------------------+-----------------+------------+--------------+
             Early deployment
             train for         End of Engineering
             ISP/Telco/PTT
   11.3DB    xDSL broadband
             concentrator
             platform, (NRP)   Upgrade recommended to 12.1(4)DB1
             for 6400
+----------+------------------+-----------------+------------+--------------+
             Short-lived ED    End of Engineering
   11.3HA    release for ISR
             3300 (SONET/SDH
             router)           Upgrade recommended to 12.0
+----------+------------------+-----------------+------------+--------------+
             MC3810            Not available
   11.3MA    functionality
             only              Not scheduled
+----------+------------------+-----------------+------------+--------------+
             Voice over IP,    End of Engineering
   11.3NA    media
             convergence,
             various platforms Upgrade recommended to 12.0(5)T
+----------+------------------+-----------------+------------+--------------+
             Early deployment  End of Engineering
    11.3T    major release,
             feature-rich for
             early adopters    Upgrade recommended to 12.0(17)
+----------+------------------+-----------------+------------+--------------+
             Multilayer
             Switching and
             Multiprotocol     End of Engineering
             over ATM
   11.3WA4   functionality for
             Catalyst 5000
             RSM, 4500, 4700,  Upgrade recommended
             7200, 7500,
             LightStream 1010
+----------+------------------+-----------------+------------+--------------+
                               End of Engineering
  11.3(2)XA  Introduction of
             ubr7246 and 2600  Upgrade recommended
+===========================================================================+
      12.0-based Releases           Rebuild         Interim    Maintenance
+===========================================================================+
             General
    12.0     deployment                                        12.0(17)
             release for all                                   2001-Apr-23
             platforms
+----------+------------------+-----------------+------------+--------------+
                               Unavailable
   12.0DA    xDSL support:
             6100, 6200        Upgrade recommended to 12.1(5)DA1
+----------+------------------+-----------------+------------+--------------+
             Early Deployment
             (ED) release,
             which delivers    Unavailable
             support for the
   12.0DB    Cisco 6400
             Universal Access
             Concentrator
             (UAC) for Node    Upgrade recommended to 12.1(4)DB1
             Switch Processor
             (NSP)
+----------+------------------+-----------------+------------+--------------+
             Early Deployment
             (ED) release,
             which delivers    Unavailable
             support for the
   12.0DC    Cisco 6400
             Universal Access
             Concentrator
             (UAC) for Node    Upgrade recommended to 12.1(5)DC
             Route Processor
             (NRP)
+----------+------------------+-----------------+------------+--------------+
                               12.0(15)S3,                     12.0(17)S
                               12.0(16)S1         12.0(16.06)S 2001-May-07
    12.0S    Core/ISP support:
             GSR, RSP, c7200   2001-April-23
                               2001-April-30
+----------+------------------+-----------------+------------+--------------+
   12.0SC    Cable/broadband   Not vulnerable
             ISP: ubr7200
+----------+------------------+-----------------+------------+--------------+
   12.0SL    10000 ESR: c10k   Not vulnerable
+----------+------------------+-----------------+------------+--------------+
             Cisco IOS
             software
             Release12.0ST is
             an early
             deployment (ED)
   12.0ST    release for the   Not vulnerable
             Cisco 7200,
             7500/7000RSP and
             12000 (GSR)
             series routers
             for Service
             Providers (ISPs).
+----------+------------------+-----------------+------------+--------------+
             Early
             Deployment(ED):
    12.0T    VPN, Distributed                                  12.0(5)T
             Director, various
             platforms
+----------+------------------+-----------------+------------+--------------+
             Catalyst
             switches:          12.0(10)W5(18g)
             cat2948g-l3,      2001-Apr-20
             cat4232
   12.0W5  +------------------+-----------------+------------+--------------+
             cat8510c,
             cat8540c, c6msm,                                   12.0(16)W5(21)
             ls1010, cat8510m,
             cat8540m, c5atm                                   2001-May-21
+----------+------------------+-----------------+------------+--------------+
             Catalyst
   12.0WT    switches:         Not vulnerable
             cat4840g
+----------+------------------+-----------------+------------+--------------+
             Early Deployment  Unavailable
   12.0XA    (ED): limited     Upgrade recommended to 12.1(8), available
             platforms         2001-Apr-23
+----------+------------------+-----------------+------------+--------------+
             Short-lived early Unavailable
   12.0XB    deployment        Upgrade recommended to 12.1(8), available
             release           2001-Apr-23
+----------+------------------+-----------------+------------+--------------+
             Early Deployment  Unavailable
   12.0XC    (ED): limited     Upgrade recommended to 12.1(8), available
             platforms         2001-Apr-23
+----------+------------------+-----------------+------------+--------------+
             Early Deployment  Unavailable
   12.0XD    (ED): limited     Upgrade recommended to 12.1(8), available
             platforms         2001-Apr-23
+----------+------------------+-----------------+------------+--------------+
             Early Deployment
   12.0XE    (ED): limited     Not Vulnerable
             platforms
+----------+------------------+-----------------+------------+--------------+
             Early Deployment  Unavailable
   12.0XF    (ED): limited     Upgrade recommended to 12.1(8), available
             platforms         2001-Apr-23
+----------+------------------+-----------------+------------+--------------+
             Early Deployment  Unavailable
   12.0XG    (ED): limited     Upgrade recommended to 12.1(8), available
             platforms         2001-Apr-23
+----------+------------------+-----------------+------------+--------------+
             Early Deployment  Unavailable
   12.0XH    (ED): limited     Upgrade recommended to 12.1(8), available
             platforms         2001-Apr-23
+----------+------------------+-----------------+------------+--------------+
             Early Deployment  Unavailable
   12.0XI    (ED): limited     Upgrade recommended to 12.1(8), available
             platforms         2001-Apr-23
+----------+------------------+-----------------+------------+--------------+
             Early Deployment  Unavailable
   12.0XJ    (ED): limited     Upgrade recommended to 12.1(8), available
             platforms         2001-Apr-23
+----------+------------------+-----------------+------------+--------------+
             Early Deployment
   12.0XK    (ED): limited     Not vulnerable
             platforms
+----------+------------------+-----------------+------------+--------------+
             Early Deployment
   12.0XL    (ED): limited     Not vulnerable
             platforms
+----------+------------------+-----------------+------------+--------------+
             Short-lived early
   12.0XM    deployment        Not vulnerable
             release
+----------+------------------+-----------------+------------+--------------+
             Early Deployment
   12.0XN    (ED): limited      Not vulnerable
             platforms
+----------+------------------+-----------------+------------+--------------+
             Early Deployment
   12.0XP    (ED): limited     Not vulnerable
             platforms
+----------+------------------+-----------------+------------+--------------+
             Short-lived early
   12.0XQ    deployment        Not vulnerable
             release
+----------+------------------+-----------------+------------+--------------+
             Short-lived early
   12.0XR    deployment        Not vulnerable
             release
+----------+------------------+-----------------+------------+--------------+
             Short-lived early
   12.0XS    deployment        Not vulnerable
             release
+----------+------------------+-----------------+------------+--------------+
             Early Deployment
   12.0XU    (ED): limited     Not vulnerable
             platforms
+----------+------------------+-----------------+------------+--------------+
             Short-lived early
   12.0XV    deployment        Not vulnerable
             release
+===========================================================================+
     12.1-based and Later
           Releases                 Rebuild         Interim    Maintenance
+===========================================================================+
             General
    12.1     deployment         Not vulnerable
             release for all
             platforms
+===========================================================================+
                                      Notes
+===========================================================================+
 * All dates are estimated and subject to change.

 ** Interim releases are subjected to less rigorous testing than regular
 maintenance releases, and may have serious bugs.
+===========================================================================+

Getting Fixed Software

Cisco is offering free software upgrades to remedy this vulnerability for
all affected customers.

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

Customers without contracts 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

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

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

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

There are no known workarounds for this vulnerablity.  Please upgrade to
fixed versions.

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

Cisco has had no reports of malicious exploitation of this vulnerability.
The failure was discovered  because of a malfunction in the BGP
implementation of another vendor, which caused a series of crashes that led
to the identification of this issue.

Cisco knows of no public announcements of this vulnerability before the
date of this notice.

Status of This Notice: FINAL
============================

This is a final notice. Although Cisco cannot guarantee the accuracy of all
statements in this notice, all of the facts have been checked to the best
of our ability.   Cisco does not anticipate issuing updated versions of
this notice unless there is some material change in the facts. Should there
be a significant change in the facts, Cisco may update this notice.


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

This notice will be posted on Cisco's Worldwide Web site at
http://www.cisco.com/warp/public/707/ios-bgp-attr-corruption-pub.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
   * bugtraq@securityfocus.com
   * firewalls@lists.gnac.com
   * first-teams@first.org (includes CERT/CC)
   * cisco@spot.colorado.edu
   * cisco-nsp@puck.nether.net
   * comp.dcom.sys.cisco
   * Various internal Cisco mailing lists

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

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

 Revision Number1.0  Initial 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
Web site at
http://www.cisco.com/warp/public/707/sec_incident_response.shtml. This
includes instructions for press inquiries regarding Cisco security notices.

  ------------------------------------------------------------------------

This notice is Copyright 2001 by Cisco Systems, Inc. This notice may be
redistributed freely after the release date given at the top of the text,
provided that redistributed copies are complete and unmodified, and include
all date and version information.

  ------------------------------------------------------------------------

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