The implementation of a Border Gateway Protocol route that contains an experimental attribute exposed a bug in Cisco IOS XR Software, resulting in session terminations and causing a temporary denial of service condition.
A recent route addition by the RIPE NCC Routing Information Service (RIS) exposed a flaw in Cisco IOS XR Software due to improper processing of experimental Border Gateway Protocol (BGP) route attributes. The event occurred around 8:40 GMT (3:40 a.m. EST) on Friday, August 27, 2010. The implementation of the BGP route that contains an experimental attribute, type code 99, caused devices running Cisco IOS-XR Software to close some BGP sessions with BGP peers, resulting in a temporary denial of service condition.
The error caused some BGP peers to temporarily lose access to the Internet or stop exchanging BGP route information. The condition persisted for as long as 30 minutes, until RIS removed the route addition.
The route processing exposed a bug in Cisco IOS XR Software, identified as bug ID CSCti62211, documented in IntelliShield alert 21266.
Potential exposure to malicious exploitation of this flaw is low. Because of the existing BGP infrastructure, a host must be manually added to the list of BGP neighbors to exchange route information with BGP peers. However, the error condition could arise during other types of experimental or unusual route additions with authorized peers.
Cisco PSIRT has released a security advisory at the following link: cisco-sa-20100827-bgp. Software updates are not yet available.
The security vulnerability applies to the following combinations of products.
Security Activity Bulletin
Original Release Base
The urgency and severity ratings of this alert are not tailored to individual users; users may value alerts differently based upon their network configurations and circumstances. THE ALERT, AND INFORMATION CONTAINED THEREIN, ARE PROVIDED ON AN "AS IS" BASIS AND DO NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE ALERT, AND INFORMATION CONTAINED THEREIN, OR MATERIALS LINKED FROM THE ALERT, IS AT YOUR OWN RISK. INFORMATION IN THIS ALERT AND ANY RELATED COMMUNICATIONS IS BASED ON OUR KNOWLEDGE AT THE TIME OF PUBLICATION AND IS SUBJECT TO CHANGE WITHOUT NOTICE. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE ALERTS AT ANY TIME.