Red Hat Enterprise Linux 4 does not properly compile and link gdm with tcp_wrappers on x86_64 platforms, which might allow remote attackers to bypass intended access restrictions.
Red Hat is aware of this issue and is tracking it via the following bug: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=181302
An update has been released which resolves this issue:
http://rhn.redhat.com/errata/RHSA-2010-0657.html