Multiple use-after-free vulnerabilities in PHP before 5.4.45, 5.5.x before 5.5.29, and 5.6.x before 5.6.13 allow remote attackers to execute arbitrary code via vectors related to (1) the Serializable interface, (2) the SplObjectStorage class, and (3) the SplDoublyLinkedList class, which are mishandled during unserialization.
http://php.net/ChangeLog-5.php
https://bugs.php.net/bug.php?id=70172
https://bugs.php.net/bug.php?id=70365
https://bugs.php.net/bug.php?id=70366
https://security.gentoo.org/glsa/201606-10