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.