D-BUS (dbus) before 0.22 does not properly restrict access to a socket, if the socket address is known, which allows local users to listen or send arbitrary messages on another user's per-user session bus via that socket.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10973
http://www.securityfocus.com/bid/12435
http://www.redhat.com/support/errata/RHSA-2005-102.html
http://www.mandriva.com/security/advisories?name=MDKSA-2005:105
http://www.auscert.org.au/render.html?it=5156
http://securitytracker.com/id?1013075
http://secunia.com/advisories/15844
http://secunia.com/advisories/15833