libxpc in Apple iOS before 8.4.1 and OS X before 10.10.5 allows attackers to execute arbitrary code in a privileged context or cause a denial of service (memory corruption) via a crafted app that sends a malformed XPC message.
https://support.apple.com/kb/HT205031
https://support.apple.com/kb/HT205030
http://www.securitytracker.com/id/1033275
http://www.securityfocus.com/bid/76343
http://lists.apple.com/archives/security-announce/2015/Aug/msg00002.html
http://lists.apple.com/archives/security-announce/2015/Aug/msg00001.html