This issue affected Firefox and Thunderbird as shipped with Red Hat Enterprise Linux 4. Red Hat Enterprise Linux 2.1 and 3 were not affected. Updated packages are available along with our advisories at the URL below and by using the Red Hat Network 'up2date' tool. https://rhn.redhat.com/cve/CVE-2006-1724.html
The vendor has not provided us with any further information regarding this vulnerability.