The TCP implementation in the kernel in Apple iOS before 8.3, Apple OS X before 10.10.3, and Apple TV before 7.2 does not properly implement the Urgent (aka out-of-band data) mechanism, which allows remote attackers to cause a denial of service via crafted packets.
lists.apple.com/archives/security-announce/2015/Apr/msg00001.html
lists.apple.com/archives/security-announce/2015/Apr/msg00002.html
lists.apple.com/archives/security-announce/2015/Apr/msg00003.html
www.securitytracker.com/id/1032048
support.apple.com/HT204659
support.apple.com/HT204661
support.apple.com/HT204662
support.apple.com/kb/HT204870