Passcode Lock in Apple iOS before 7 does not properly manage the lock state, which allows physically proximate attackers to bypass an intended passcode requirement by leveraging a race condition involving phone calls and ejection of a SIM card.
http://support.apple.com/kb/HT5934
http://secunia.com/advisories/54886
http://lists.apple.com/archives/security-announce/2013/Sep/msg00006.html