The Neighbor Discovery (ND) protocol implementation in the IPv6 stack in Cisco IOS 15.3(3)S0.1 on ASR devices mishandles internal tables, which allows remote attackers to cause a denial of service (memory consumption or device crash) via a flood of crafted ND messages, aka Bug ID CSCup28217.
http://www.securitytracker.com/id/1034432
http://www.securityfocus.com/bid/79200
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151214-ios