CFNetwork in Apple iOS before 6 does not properly identify the host portion of a URL, which allows remote attackers to obtain sensitive information by leveraging the construction of an HTTP request with an incorrect hostname derived from a malformed URL.
https://exchange.xforce.ibmcloud.com/vulnerabilities/78723
http://support.apple.com/kb/HT5503
http://lists.apple.com/archives/security-announce/2012/Sep/msg00003.html