The BGP implementation in Cisco IOS 15.2, IOS XE 3.5.xS before 3.5.2S, and IOS XR 4.1.0 through 4.2.2 allows remote attackers to cause a denial of service (multiple connection resets) by leveraging a peer relationship and sending a malformed attribute, aka Bug IDs CSCtt35379, CSCty58300, CSCtz63248, and CSCtz62914.
http://www.securitytracker.com/id?1027576
http://www.securityfocus.com/bid/55694
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120926-bgp