Some people have published a Linux security kernel patch. But as The Register reports, they will not explain the vulnerability to you unless you certify that you are not an American:

So what's all this got to do with Red Hat? Well, non-qualifying people, we can't exactly tell you that. But when we asked Red Hat about it we got an official comment which at least partially explains it: "RHSA-2002-158 is an errata kernel which addresses certain security vulnerabilities. Quite simply, these vulnerabilities were discovered and documented by ppl outside of the US, and due to the Digital Millenium Copyright Act legislation in the US, it is potentially dangerous to disclose any information on security vulnerabilities, which may also be used in order to circumvent digital security - i.e. computer security. For this reason, RH cannot publish this security information, as it is not available from the community in the first instance. The www.thefreeworld.net site allows for accessing this information, but requires you agree to terms which protect the author and documenter of the patches from being accusations that they themselves have breached DMCA."

Check out this Red Hat page.

(thanks to Adam Flinton for the heads-up on this)