The Sorenson codec in QuickTime in Apple Mac OS X before 10.7.5, and in CoreMedia in iOS before 6, accesses uninitialized memory locations, which allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via a crafted movie file with Sorenson encoding.
Apple Security Advisory 2012-09-24-1 - Apple TV 5.1 is now available and addresses issues relating to malicious media loading, memory corruption, and more.