In this particular case, RedHat has posted some fixes for "potential security holes" on its web site, but the explanation of why these are security holes cannot be provided to US eyes lest they violate the DMCA.
So the details have been provided to a web site in the UK, which has copyrighted them, and has instituted a mechanism (a click-thru license agreement) that controls access to the information. As shown in the article above, the license agreement specifically states that if you are in the USA, you are not allowed in.
Under the DMCA, it is illegal for those of us in the USA to represent that we are NOT in the USA, for the purpose of reading the details, since that would circumvent a technological measure used to control access to a copyrighted work.
Now, do you see how stupid this is?