Apache QPID 0.14, 0.16, and earlier uses a NullAuthenticator mechanism to authenticate catch-up shadow connections to AMQP brokers, which allows remote attackers to bypass authentication.
Apache Qpid 0.12 does not properly verify credentials during the joining of a cluster, which allows remote attackers to obtain access to the messaging functionality and job functionality of a cluster by leveraging knowledge of a cluster-username.