Cisco Systems Inc. Information for VU#106392

Cisco IOS vulnerable to DoS via unrecognized transitive attribute in BGP UPDATE

Status

Affected

Vendor Statement

For more information, see the Cisco advisory.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Vendor References

None

Addendum

-----BEGIN PGP SIGNED MESSAGE-----

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 IOSŪ 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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