Cisco IOS 12.2, 12.4, 15.0, 15.1, 15.2, 15.3, and 15.4 and IOS XE 2.5.x, 2.6.x, 3.1.xS through 3.12.xS before 3.12.3S, 3.2.xE through 3.7.xE before 3.7.1E, 3.3.xSG, 3.4.xSG, and 3.13.xS before 3.13.2S allow remote attackers to cause a denial of service (device reload) by sending malformed IKEv2 packets over (1) IPv4 or (2) IPv6, aka Bug ID CSCum36951.