Vulnerability Note VU#106392

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

Overview

There is a denial-of-service vulnerability in several specific but common configurations of Cisco IOS.

I. Description

There is a problem involving BGP updates on Cisco routers with BGP4 Prefix Filtering and Inbound Route Maps enabled. A route update with an unrecognized transitive attribute may cause vulnerable routers to crash. This problem does not appear to have been exploited intentionally by attackers, but it has occurred accidentally during normal operation as the result of interaction with another vendor's product.

More information on this problem is available from Cisco at:

http://www.cisco.com/warp/public/707/ios-bgp-attr-corruption-pub.shtml

II. Impact

Attackers that are able to send malformed BGP updates can cause vulnerable routers to crash causing network outages. Under certain circumstances, an attacker may be able to use the BGP infrastructure to propogate the bad route update to multiple routers.

III. Solution

Cisco has released an advisory that provides a list of affected products, along with instructions for obtaining fixed software. Because there are many possible combinations of hardware and software configurations, the CERT/CC recommends that all users of IOS and software consult the following Cisco Security Advisory:

http://www.cisco.com/warp/public/707/ios-bgp-attr-corruption-pub.shtml

Systems Affected

Vendor	Status	Date Updated
Cisco Systems Inc.	Vulnerable	10-May-2001

References

http://www.cisco.com/warp/public/707/ios-bgp-attr-corruption-pub.shtml
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/ip_c/ipcprt2/1cdbgp.htm#xtocid124918
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/ip_c/ipcprt2/1cdbgp.htm#xtocid124934
http://www.securityfocus.com/bid/2733

Credit

The CERT/CC would like to thank Cisco Systems for providing a description of this vulnerability and a patch to address it.

This document was written by Ian A. Finlay and is based on information obtained from a Cisco Security Advisory.

Other Information

Date Public	05/10/2001
Date First Published	05/10/2001 05:10:31 PM
Date Last Updated	04/09/2003
CERT Advisory
CVE Name	CVE-2001-0650
Metric	21.55
Document Revision	27

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