Mozilla Network Security Services (NSS) before 3.19, as used in Mozilla Firefox before 39.0, Firefox ESR 31.x before 31.8 and 38.x before 38.1, Thunderbird before 38.1, and other products, does not properly determine state transitions for the TLS state machine, which allows man-in-the-middle attackers to defeat cryptographic protection mechanisms by blocking messages, as demonstrated by removing a forward-secrecy property by blocking a ServerKeyExchange message, aka a "SMACK SKIP-TLS" issue.
https://security.gentoo.org/glsa/201701-46
https://security.gentoo.org/glsa/201512-10
https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/NSS_3.19_release_notes
http://www.ubuntu.com/usn/USN-2673-1
http://www.ubuntu.com/usn/USN-2672-1
http://www.ubuntu.com/usn/USN-2656-2
http://www.ubuntu.com/usn/USN-2656-1
http://www.securitytracker.com/id/1032784
http://www.securitytracker.com/id/1032783
http://www.securityfocus.com/bid/91787
http://www.securityfocus.com/bid/83398
http://www.securityfocus.com/bid/75541
http://www.oracle.com/technetwork/topics/security/ovmbulletinjul2016-3090546.html
http://www.oracle.com/technetwork/topics/security/bulletinoct2015-2511968.html
http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html
http://www.oracle.com/technetwork/security-advisory/cpujul2016-2881720.html
http://www.oracle.com/technetwork/security-advisory/cpuapr2016v3-2985753.html
http://www.mozilla.org/security/announce/2015/mfsa2015-71.html
http://www.debian.org/security/2015/dsa-3336
http://www.debian.org/security/2015/dsa-3324
http://rhn.redhat.com/errata/RHSA-2015-1664.html
http://rhn.redhat.com/errata/RHSA-2015-1185.html
http://lists.opensuse.org/opensuse-security-announce/2015-08/msg00021.html
http://lists.opensuse.org/opensuse-security-announce/2015-07/msg00034.html
http://lists.opensuse.org/opensuse-security-announce/2015-07/msg00033.html
http://lists.opensuse.org/opensuse-security-announce/2015-07/msg00031.html
http://lists.opensuse.org/opensuse-security-announce/2015-07/msg00025.html