The exception::getTraceAsString function in Zend/zend_exceptions.c in PHP before 5.4.40, 5.5.x before 5.5.24, and 5.6.x before 5.6.8 allows remote attackers to execute arbitrary code via an unexpected data type, related to a "type confusion" issue.
http://php.net/ChangeLog-5.php
http://rhn.redhat.com/errata/RHSA-2015-1135.html
http://rhn.redhat.com/errata/RHSA-2015-1186.html
http://rhn.redhat.com/errata/RHSA-2015-1187.html
http://rhn.redhat.com/errata/RHSA-2015-1218.html
https://bugs.php.net/bug.php?id=69152
http://www.openwall.com/lists/oss-security/2015/06/16/12
http://www.oracle.com/technetwork/topics/security/linuxbulletinjan2016-2867209.html