The Data Security component in Apple iOS before 5 and Apple TV before 4.4 does not properly restrict use of the MD5 hash algorithm within X.509 certificates, which makes it easier for man-in-the-middle attackers to spoof servers or obtain sensitive information via a crafted certificate.
https://exchange.xforce.ibmcloud.com/vulnerabilities/70547
http://support.apple.com/kb/HT5001
http://support.apple.com/kb/HT4999
http://lists.apple.com/archives/security-announce/2013/Oct/msg00004.html
http://lists.apple.com/archives/Security-announce/2011//Oct/msg00002.html
http://lists.apple.com/archives/Security-announce/2011//Oct/msg00001.html