http://www.daemonology.net/hyperthreading-considered-harmful/ describes a timing attack against certain processors where a local user can cause an information leak from applications. This could allow, for example, an untrusted local user to gain access to portions of cryptographic keys. Note that for an attack to be sucessful you need to be running on an affected processor, have a malicious local user, and be doing operations with a valuable private key. The OpenSSL team are working on a patch that will mitigate this issue and remove the ability to do timing attacks (of any nature) on private key operations. We will look at backporting and applying this patch and producing OpenSSL updates.
(Just to clarify, we'll also be taking a look at other packages that deal with private key operations that may be susceptable to similar attacks)
From a D.J.Bernstein posting on comp.arch: ... Osvik and Tromer made clear months ago that hyperthreading needed to be turned off for security. They've been advertising information disclosure through hyperthreading since at least February. See, for example, the ``Other People's Cache---HyperAttacks with HyperThreading'' abstract in http://www.esat.kuleuven.ac.be/sista-cosic-docarch/template.php?page=activities ...
Fixed in FC development.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on the solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2005-476.html