ext/wddx/wddx.c in PHP before 5.6.25 and 7.x before 7.0.10 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) or possibly have unspecified other impact via an invalid wddxPacket XML document that is mishandled in a wddx_deserialize call, as demonstrated by a stray element inside a boolean element, leading to incorrect pop processing.
https://www.tenable.com/security/tns-2016-19
https://security.gentoo.org/glsa/201611-22
https://github.com/php/php-src/commit/a14fdb9746262549bbbb96abb87338bacd147e1b?w=1
https://github.com/php/php-src/commit/0c8a2a2cd1056b7dc403eacb5d2c0eec6ce47c6f
http://www.securitytracker.com/id/1036680
http://www.securityfocus.com/bid/92767
http://www.php.net/ChangeLog-7.php
http://www.php.net/ChangeLog-5.php