CSS Letter-Spacing Heap Overflow Vulnerability An anonymous researcher for TippingPoint and the Zero Day Initiative discovered an integer overflow triggered by the CSS letter-spacing property. This results in in under-allocating memory and ultimately a heap buffer overflow which could be exploited to run code of the attacker's choice. The overflow condition itself does not require JavaScript and thus could affect Thunderbird via received mail, but without scripting to prepare memory it may not be possible to exploit this condition in mail. Workaround Upgrade to the fixed version. References [1]ZDI-06-009 [2]https://bugzilla.mozilla.org/show_bug.cgi?id=325403 This issue also affects FC4
These issues have been resolved in FEDORA-2006-411 for FC5 and FEDORA-2006-410 for FC4