Memory leak in Cisco IOS 12.4, 15.0, and 15.1, and IOS XE 2.5.x through 3.2.x, allows remote attackers to cause a denial of service (memory consumption) via a crafted SIP message, aka Bug ID CSCti48504.
http://www.cisco.com/en/US/products/products_security_advisory09186a0080b95d5a.shtml
http://tools.cisco.com/security/center/viewAlert.x?alertId=24130