The kernel in Apple iOS before 9.3, tvOS before 9.2, and watchOS before 2.2 does not properly restrict the execute permission, which allows attackers to bypass a code-signing protection mechanism via a crafted app.
https://support.apple.com/HT206169
https://support.apple.com/HT206168
https://support.apple.com/HT206166
http://www.securitytracker.com/id/1035353
http://lists.apple.com/archives/security-announce/2016/Mar/msg00002.html
http://lists.apple.com/archives/security-announce/2016/Mar/msg00001.html
http://lists.apple.com/archives/security-announce/2016/Mar/msg00000.html