TrueTypeScaler in Apple iOS before 9.3, OS X before 10.11.4, tvOS before 9.2, and watchOS before 2.2 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted font file.
https://support.apple.com/HT205641
https://support.apple.com/HT205640
https://support.apple.com/HT205637
https://support.apple.com/HT205635
http://www.zerodayinitiative.com/advisories/ZDI-16-204
http://www.securitytracker.com/id/1035353
http://lists.apple.com/archives/security-announce/2015/Dec/msg00005.html
http://lists.apple.com/archives/security-announce/2015/Dec/msg00002.html
http://lists.apple.com/archives/security-announce/2015/Dec/msg00001.html
http://lists.apple.com/archives/security-announce/2015/Dec/msg00000.html