The host is installed with php through 5.5.20 or 5.6.x through 5.6.4 and is prone to a double free vulnerability. The flaw is present in the in the zend_ts_hash_graceful_destroy function in zend_ts_hash.c in the Zend Engine, which fails to properly handle unknown vectors. Successful exploitation allows remote attackers to cause a denial of service or possibly have unspecified other impact.