From MFSA 2008-42: Mozilla developers identified and fixed several stability bugs in the browser engine used in Firefox and other Mozilla-based products. Some of these crashes showed evidence of memory corruption under certain circumstances and we presume that with enough effort at least some of these could be exploited to run arbitrary code. David Maciejak and Drew Yao reported crashes in graphics rendering which only affected Firefox 3.
This is now public
This was addressed via: Red Hat Enterprise Linux version 4 (RHSA-2008:0879) Red Hat Enterprise Linux version 5 (RHSA-2008:0879)