The Passcode Lock implementation in Apple iOS before 6 allows physically proximate attackers to bypass an intended passcode requirement via vectors related to ending a FaceTime call.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2012-3683
http://support.apple.com/kb/HT5503
http://lists.apple.com/archives/security-announce/2012/Sep/msg00003.html