The single best source of information, especially with respect to bugs or problems with the Red Hat Linux distribution are the errata pages available at http://www.redhat.com/errata and look for both the General Errata and the platform-specific Errata for your version of Red Hat Linux. (See also E.4 (Resources Section) for other ways to get the Errata).
It may seem strange that we list this as the very first item, but the errata pages are perhaps the best resource for fixing 90% of the common problems with Red Hat Linux. Security holes for which there is a solution are generally on the errata page 24 hours after Red Hat has been notified.
You should always check there first.