Deserialization of untrusted data in Apache Mina

ZDRES-232: resolveProxyClass Not Overridden - acceptMatchers Filter Bypass via java.lang.reflect.Proxy Assessment: Fully addressed. When the serialised stream contains a TC_PROXYCLASSDESC (the marker for a java.lang.reflect.Proxy ), JDK’s ObjectInputStream.readProxyDesc() is dispatched. JDK then calls the default ObjectInputStream.resolveProxyClass(interfaces) implementation, which performs Class.forName(intf, false, latestUserDefinedLoader()) for EACH interface name and constructs the proxy class — bypassing the accepted classes list . ZDRES-233: Class.forName(name, initialize=true, classLoader) in readClassDescriptor Triggers Static Initialiser of Allow-Listed Classes Assessment: Fully addressed. For ANY class on the allow-list, deserialising a stream that names it triggers the class’s (static initialiser) BEFORE any instance is constructed. This means an attacker who supplies a class name on the allow-list (e.g., the developer wrote accept(“com.myapp.*") , attacker supplies com.myapp.SomeClass ) causes <clinit> of SomeClass — and many real-world classes have side-effecting static initialisers Both issues have been fixed.