The kernel in Apple iOS before 7 uses an incorrect data size for a certain integer variable, which allows attackers to cause a denial of service (infinite loop and device hang) via a crafted application, related to an "integer truncation vulnerability."
http://lists.apple.com/archives/security-announce/2013/Oct/msg00004.html
http://lists.apple.com/archives/security-announce/2013/Sep/msg00006.html