Vulnerability Note VU#689326

Cisco IOS vulnerable to DoS via malformed BGP packet

Original Release date: 26 Jan 2005 | Last revised: 26 Jan 2005


A vulnerability in Cisco's Internetwork Operating System (IOS) could result in a remotely exploitable denial of service.


Cisco Internetwork Operating System (IOS) includes support for Border Gateway Protocol (BGP), which is defined in RFC 1771. BGP is designed to exchange network reachability information between peer nodes. Information advertised by a BGP system to its peers includes timers, metrics, and paths to different Autonomous System (AS) networks. Routing between AS networks depends on BGP, and the Internet is a network of AS networks. Therefore, vulnerabilities in BGP have the potential to affect the Internet infrastructure.

A Cisco device running IOS that is enabled for BGP is vulnerable to a denial-of-service attack via a malformed BGP packet. The specific nature of the crafted packets exploiting this vulnerability is not known. IOS is vulnerable only if the device is set up with the bgp log-neighbor-changes command.


By sending a specially crafted BGP packet to an affected device, a remote attacker could cause the device to reload. Repeated exploitation of this vulnerability could result in a denial-of-service condition. Because BGP must be configured to accept traffic from an explicitly defined peer, exploitation would be difficult from an untrusted host.


Apply a patch or upgrade
Please refer to the "Software Versions and Fixes" section of the Cisco Security Advisory for more information on upgrading.


Cisco recommends a number of workarounds. For a complete list of workarounds, see the "Workarounds" section of the Cisco Security Advisory.

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
Cisco Systems Inc.Affected-26 Jan 2005
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



Thanks to Cisco PSIRT for reporting this vulnerability.

This document was written by Will Dormann.

Other Information

  • CVE IDs: Unknown
  • Date Public: 26 Jan 2005
  • Date First Published: 26 Jan 2005
  • Date Last Updated: 26 Jan 2005
  • Severity Metric: 12.13
  • Document Revision: 11


If you have feedback, comments, or additional information about this vulnerability, please send us email.