The X Display Manager Control Protocol (XDMCP) support for GDM before 2.4.1.6 allows attackers to cause a denial of service (daemon crash) via a short authorization key name.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A129
http://www.redhat.com/support/errata/RHSA-2003-259.html
http://www.redhat.com/support/errata/RHSA-2003-258.html
http://mail.gnome.org/archives/gnome-hackers/2003-August/msg00045.html
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000729