ext/mysqlnd/mysqlnd.c in PHP before 5.4.43, 5.5.x before 5.5.27, and 5.6.x before 5.6.11 uses a client SSL option to mean that SSL is optional, which allows man-in-the-middle attackers to spoof servers via a cleartext-downgrade attack, a related issue to CVE-2015-3152.
https://bugs.php.net/bug.php?id=69669
http://www.ubuntu.com/usn/USN-2952-2
http://www.ubuntu.com/usn/USN-2952-1
http://php.net/ChangeLog-5.php
http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00058.html
http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00057.html
http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00056.html
http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00052.html
http://git.php.net/?p=php-src.git%3Ba=commit%3Bh=97aa752fee61fccdec361279adbfb17a3c60f3f4