RabbitMQ Java client: Unvalidated Class.forName in JSON-RPC ProcedureDescription enables arbitrary class loading

The JSON-RPC tools in com.rabbitmq.tools.jsonrpc perform Class.forName(javaReturnType) with initialize=true on class names received from untrusted AMQP messages, without any validation or allowlist. Vulnerable code (ProcedureDescription.java:101-127): When a JsonRpcClient connects, ...