The NSURL implementation in the CFNetwork SSL component in Apple iOS before 9 does not properly verify X.509 certificates from SSL servers after a certificate change, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate.
lists.apple.com/archives/security-announce/2015/Sep/msg00001.html
lists.apple.com/archives/security-announce/2015/Sep/msg00005.html
lists.apple.com/archives/security-announce/2015/Sep/msg00008.html
www.securityfocus.com/bid/76764
www.securitytracker.com/id/1033609
support.apple.com/HT205212
support.apple.com/HT205213
support.apple.com/HT205267