The default configuration of the pam_xauth module forwards MIT-Magic-Cookies to new X sessions, which could allow local users to gain root privileges by stealing the cookies from a temporary .xauth file, which is created with the original user's credentials after root uses su.
http://www.securityfocus.com/bid/6753
http://www.redhat.com/support/errata/RHSA-2003-035.html
http://www.redhat.com/support/errata/RHSA-2003-028.html
http://www.mandrakesoft.com/security/advisories?name=MDKSA-2003:017
http://www.kb.cert.org/vuls/id/911505
http://www.iss.net/security_center/static/11254.php
http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsalert/55760
http://marc.info/?l=bugtraq&m=104431622818954&w=2
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000693