[Full-Disclosure] CERT Advisory CA-2003-15 Cisco IOS Interface Blocked by IPv4 Packet (fwd)

From: Muhammad Faisal Rauf Danka (mfrd_at_attitudex.com)
Date: 07/17/03

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Date: Thu, 17 Jul 2003 01:48:34 -0700 (PDT)
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    Muhammad Faisal Rauf Danka

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    Date: Thu, 17 Jul 2003 00:11:09 -0400
To: cert-advisory@cert.org

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    CERT Advisory CA-2003-15 Cisco IOS Interface Blocked by IPv4 Packet

       Original release date: July 16, 2003
       Last revised: --
       Source: CERT/CC

       A complete revision history can be found at the end of this file.

    Systems Affected

         * All Cisco devices running Cisco IOS software and configured to
           process Internet Protocol version 4 (IPv4) packets

    Overview

       A vulnerability in many versions of Cisco IOS could allow an intruder
       to execute a denial-of-service attack against a vulnerable device.

    I. Description

       Cisco IOS is a very widely deployed network operating system. A
       vulnerability in IOS could allow an intruder to execute a
       denial-of-service attack against an affected device. Cisco has
       published an advisory on this topic, available at
       http://www.cisco.com/warp/public/707/cisco-sa-20030717-blocked.shtml
       We strongly encourage sites using IOS to read this document and take
       appropriate action.

       The CERT/CC is tracking this issue as VU#411332. This reference number
       corresponds to CVE candidate CAN-2003-0567.

    II. Impact

       By sending specially crafted IPv4 packets to an interface on a
       vulnerable device, an intruder can cause the device to stop processing
       packets destined to that interface. Quoting from Cisco's advisory:

       "A device receiving these specifically crafted IPv4 packets will force
       the inbound interface to stop processing traffic. The device may stop
       processing packets destined to the router, including routing protocol
       packets and ARP packets. No alarms will be triggered, nor will the
       router reload to correct itself. This issue can affect all Cisco
       devices running Cisco IOS software. This vulnerability may be
       exercised repeatedly resulting in loss of availability until a
       workaround has been applied or the device has been upgraded to a fixed
       version of code."

    III. Solution

    Apply a patch from Cisco

       Apply a patch as described in Cisco's Advisory.

       Until a patch can be applied, you can mitigate the risks presented by
       this vulnerability by judicious use of access control lists (ACLs).
       The correct use of ACLs depends of your network topology.
       Additionally, ACLs may degrade performace on some systems. We
       recommend reviewing the following before applying ACLs

       http://www.cisco.com/warp/public/707/cisco-sa-20030717-blocked.shtml#workarounds
       http://www.cisco.com/warp/public/707/racl.html
       http://www.cisco.com/warp/public/707/iacl.html
    _________________________________________________________________

       The CERT Coordination Center thanks Cisco Systems of for notifying us
       about this problem and for helping us to construct this advisory.
    _________________________________________________________________

       Feedback about this advisory may be directed to the author, Shawn
       Hernan
       ______________________________________________________________________

       This document is available from:
       http://www.cert.org/advisories/CA-2003-15.html
       ______________________________________________________________________

    CERT/CC Contact Information

       Email: cert@cert.org
              Phone: +1 412-268-7090 (24-hour hotline)
              Fax: +1 412-268-6989
              Postal address:
              CERT Coordination Center
              Software Engineering Institute
              Carnegie Mellon University
              Pittsburgh PA 15213-3890
              U.S.A.

       CERT/CC personnel answer the hotline 08:00-17:00 EST(GMT-5) /
       EDT(GMT-4) Monday through Friday; they are on call for emergencies
       during other hours, on U.S. holidays, and on weekends.

    Using encryption

       We strongly urge you to encrypt sensitive information sent by email.
       Our public PGP key is available from
       http://www.cert.org/CERT_PGP.key

       If you prefer to use DES, please call the CERT hotline for more
       information.

    Getting security information

       CERT publications and other security information are available from
       our web site
       http://www.cert.org/

       To subscribe to the CERT mailing list for advisories and bulletins,
       send email to majordomo@cert.org. Please include in the body of your
       message

       subscribe cert-advisory

       * "CERT" and "CERT Coordination Center" are registered in the U.S.
       Patent and Trademark Office.
       ______________________________________________________________________

       NO WARRANTY
       Any material furnished by Carnegie Mellon University and the Software
       Engineering Institute is furnished on an "as is" basis. Carnegie
       Mellon University makes no warranties of any kind, either expressed or
       implied as to any matter including, but not limited to, warranty of
       fitness for a particular purpose or merchantability, exclusivity or
       results obtained from use of the material. Carnegie Mellon University
       does not make any warranty of any kind with respect to freedom from
       patent, trademark, or copyright infringement.
         _________________________________________________________________

       Conditions for use, disclaimers, and sponsorship information

       Copyright 2003 Carnegie Mellon University.

       Revision History
    July 16, 2003: Initial release

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