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.
http://git.php.net/?p=php-src.git;a=commit;h=97aa752fee61fccdec361279adbfb17a3c60f3f4
http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00052.html
http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00056.html
http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00057.html
http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00058.html
http://php.net/ChangeLog-5.php
http://www.ubuntu.com/usn/USN-2952-1
Source: MITRE
Published: 2016-05-16
Updated: 2016-12-01
Type: CWE-284
Base Score: 4.3
Vector: AV:N/AC:M/Au:N/C:N/I:P/A:N
Impact Score: 2.9
Exploitability Score: 8.6
Severity: MEDIUM
Base Score: 5.9
Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Impact Score: 3.6
Exploitability Score: 2.2
Severity: MEDIUM