The Apache Groovy project reports:
When an application with Groovy on classpath uses standard Java
serialization mechanisms, e.g. to communicate between servers or to
store local data, it is possible for an attacker to bake a special
serialized object that will execute code directly when deserialized.
All applications which rely on serialization and do not isolate the
code which deserializes objects are subject to this vulnerability.
This is similar to CVE-2015-3253 but this exploit involves extra
wrapping of objects and catching of exceptions which are now safe
guarded against.