Memory leak in the SSL VPN feature in Cisco IOS 12.4, 15.0, and 15.1, when HTTP port redirection is enabled, allows remote attackers to cause a denial of service (memory consumption) by improperly disconnecting SSL sessions, leading to connections that remain in the CLOSE-WAIT state, aka Bug ID CSCtg21685.
http://www.cisco.com/en/US/products/products_security_advisory09186a0080b4a312.shtml