RabbitMQ: Stream listener does not enforce configured frame-size limit during authentication, permitting unauth'd mem-exhaust DoS

RabbitMQ is a messaging and streaming broker. Prior to 4.2.6, the RabbitMQ stream listener does not enforce the configured stream frame-size limit while assembling frames during authentication and before Tune negotiation, allowing an unauthenticated remote client to declare oversized frame lengths and consume broker memory in rabbit_stream_core. This issue is fixed in version 4.2.6.