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.