GraniteDS, version 3.1.1.GA, Action Message Format (AMF3) Java implementation is vulnerable to insecure deserialization

The Java implementation of GraniteDS, version 3.1.1.GA, AMF3 deserializers derives class instances from java.io.Externalizable rather than the AMF3 specification's recommendation of flash.utils.IExternalizable. A remote attacker with the ability to spoof or control an RMI server connection may be able to send serialized Java objects that execute arbitrary code when deserialized.