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 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.