The php_wddx_push_element function in ext/wddx/wddx.c in PHP before 5.6.26 and 7.x before 7.0.11 allows remote attackers to cause a denial of service (invalid pointer access and out-of-bounds read) or possibly have unspecified other impact via an incorrect boolean element in a wddxPacket XML document, leading to mishandling in a wddx_deserialize call.
https://www.tenable.com/security/tns-2016-19
https://security.gentoo.org/glsa/201611-22
https://github.com/php/php-src/commit/c4cca4c20e75359c9a13a1f9a36cb7b4e9601d29?w=1
https://access.redhat.com/errata/RHSA-2018:1296
http://www.securitytracker.com/id/1036836
http://www.securityfocus.com/bid/93011
http://www.php.net/ChangeLog-7.php