The make_http_soap_request function in ext/soap/php_http.c in PHP before 5.4.44, 5.5.x before 5.5.28, and 5.6.x before 5.6.12 does not properly retrieve keys, which allows remote attackers to cause a denial of service (NULL pointer dereference, type confusion, and application crash) or possibly execute arbitrary code via crafted serialized data representing a numerically indexed _cookies array, related to the SoapClient::__call method in ext/soap/soap.c.