Integer underflow in Apple iOS before 5.1 allows remote attackers to execute arbitrary code or cause a denial of service (device crash) via a crafted catalog file in an HFS disk image.
http://lists.apple.com/archives/security-announce/2012/Mar/msg00001.html
http://lists.apple.com/archives/security-announce/2012/May/msg00001.html
http://secunia.com/advisories/48288