The ARM prefetch abort handler in the kernel in Apple iOS before 6.1.3 and Apple TV before 5.2.1 does not ensure that it has been invoked in an abort context, which makes it easier for local users to bypass the ASLR protection mechanism via crafted code.
http://support.apple.com/kb/HT5704
http://support.apple.com/kb/HT5702
http://lists.apple.com/archives/security-announce/2013/Mar/msg00005.html
http://lists.apple.com/archives/security-announce/2013/Mar/msg00004.html