Telephony in Apple iOS before 6 uses an SMS message's return address as the displayed sender address, which allows remote attackers to spoof text communication via a message in which the return address does not match the originating address.
https://exchange.xforce.ibmcloud.com/vulnerabilities/78687
http://support.apple.com/kb/HT5503
http://lists.apple.com/archives/security-announce/2012/Sep/msg00003.html