Race condition in the VRF-aware NAT feature in Cisco IOS 12.2 through 12.4 and 15.0 through 15.2 allows remote attackers to cause a denial of service (memory consumption) via IPv4 packets, aka Bug IDs CSCtg47129 and CSCtz96745.
http://tools.cisco.com/security/center/content/CiscoSecurityNotice/CVE-2013-1142
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20130327-nat