CVE-2011-2578
Memory leak in Cisco IOS 15.1 and 15.2 allows remote attackers to cause a denial of service (memory consumption) via malformed SIP packets on a NAT interface, aka Bug ID CSCts12366.
Date published : 2012-05-02
http://www.cisco.com/en/US/docs/ios/15_1/release/notes/151-4MCAVS.html