The default configuration for Apache Qpid 0.20 and earlier, when the federation_tag attribute is enabled, accepts AMQP connections without checking the source user ID, which allows remote attackers to bypass authentication and have other unspecified impact via an AMQP request.
https://issues.apache.org/jira/browse/QPID-4631
https://bugzilla.redhat.com/show_bug.cgi?id=851355
http://secunia.com/advisories/52516