The kernel in Apple iOS before 5 and Apple TV before 4.4 does not properly recover memory allocated for incomplete TCP connections, which allows remote attackers to cause a denial of service (resource consumption) by making many connection attempts.
http://lists.apple.com/archives/Security-announce/2011//Oct/msg00001.html
http://lists.apple.com/archives/Security-announce/2011//Oct/msg00002.html
http://support.apple.com/kb/HT4999
http://support.apple.com/kb/HT5001