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 a malformed wddxPacket XML document that is mishandled in a wddx_deserialize call, as demonstrated by a tag that lacks a < (less than) character.