Stack-based buffer overflow in the openSharedCacheFile function in dyld.cpp in dyld in Apple iOS 5.1.x and 6.x through 6.1.3 makes it easier for attackers to conduct untethering attacks via a long string in the DYLD_SHARED_CACHE_DIR environment variable.
http://www.syscan.org/index.php/sg/program/day/2
http://www.securitytracker.com/id/1029054
http://support.apple.com/kb/HT5934
http://lists.apple.com/archives/security-announce/2013/Sep/msg00006.html
http://lists.apple.com/archives/security-announce/2013/Oct/msg00004.html