It was discovered that SSL connections to the MRG broker could easily be blocked. If a client or application initiated a connection to the MRG broker's listening SSL port, the client connection would block access to the port until the SSL handshake completes (or fails). If a client failed to proceed with it, then the thread was never freed to process other connections, denying service to other clients. Only SSL connections were affected by this issue, and SSL support is not enabled by default.
The fix for this issue was public a year and a half ago, but I do not know if the security implications were every really known: http://svn.apache.org/viewvc/qpid/trunk/qpid/cpp/src/qpid/sys/ssl/SslSocket.cpp?r1=790291&r2=790290&pathrev=790291&view=patch However, the second half of the above patch was reverted later: http://svn.apache.org/viewvc/qpid/trunk/qpid/cpp/src/qpid/sys/ssl/SslSocket.cpp?r1=919487&r2=938992 with the following commit message: QPID-2083: Some improvements to error handling for NSS based SSL implementation. https://issues.apache.org/jira/browse/QPID-2083 Looking at the RHEL6 and Fedora sources, the initial patch has been applied, and in RHEL6 at least the second hunk has been reverted, as with upstream (but not in Fedora).
This issue has been addressed in following products: MRG for RHEL-5 Via RHSA-2010:0756 https://rhn.redhat.com/errata/RHSA-2010-0756.html
This issue has been addressed in following products: Messaging for MRG on RHEL-4 Messaging Base for MRG on RHEL-4 Via RHSA-2010:0757 https://rhn.redhat.com/errata/RHSA-2010-0757.html