Memory leak in Cisco IOS 15.0 through 15.1, when IPS or Zone-Based Firewall (aka ZBFW) is configured, allows remote attackers to cause a denial of service (memory consumption or device crash) via vectors that trigger many session creation flows, aka Bug ID CSCti79848.
http://www.cisco.com/en/US/products/products_security_advisory09186a0080b95d57.shtml
http://tools.cisco.com/security/center/viewAlert.x?alertId=24123