The NAT implementation in Cisco IOS 12.2, 12.4, and 15.0 through 15.2 allows remote attackers to cause a denial of service (device reload) via transit IP packets, aka Bug ID CSCtr46123.
http://www.securitytracker.com/id?1027579
http://www.securityfocus.com/bid/55705
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120926-nat