A double free flaw was found in Firefox's handling of application/http-index-format documents. A malformed HTTP response could cause Firefox to execute arbitrary code with the permissions of the user running Firefox.
This is public via: http://www.mozilla.org/security/announce/2011/mfsa2011-12.html
This issue has been addressed in following products: Red Hat Enterprise Linux 6 Via RHSA-2011:0475 https://rhn.redhat.com/errata/RHSA-2011-0475.html
This issue has been addressed in following products: Red Hat Enterprise Linux 5 Red Hat Enterprise Linux 6 Red Hat Enterprise Linux 4 Via RHSA-2011:0471 https://rhn.redhat.com/errata/RHSA-2011-0471.html