Firefox 3.5 [Critical]

Affects:

• Firefox 3.5

Description

A flaw in Firefox 3.5’s Just-in-time (JIT) JavaScript compiler creates a critical vulnerability that can be used to execute malicious code.

The vulnerability can be exploited by an attacker who tricks a victim into viewing a malicious Web page containing the exploit code. The vulnerability can be mitigated by disabling the JIT in the JavaScript engine. To do so:

1. Enter about:config in the browser’s location bar.
2. Type jit in the Filter box at the top of the config editor.
3. Double-click the line containing javascript.options.jit.content setting the value to false.

Note that disabling the JIT will result in decreased JavaScript performance and is only recommended as a temporary security measure.  Once users have been received the security update containing the fix for this issue, they should restore the JIT setting to true by:

1. Enter about:config in the browser’s location bar.
2. Type jit in the Filter box at the top of the config editor.
3. Double-click the line containing javascript.options.jit.content setting the value to true.

Alternatively, users can disable the JIT by running Firefox in Safe Mode.  Windows users can do so by selecting Mozilla Firefox (Safe Mode) from the Mozilla Firefox folder.

Resolution and Availability of Patch

Version 3.5.1 of Firefox, now available on OpenLogic Exchange, addresses this issue.  If you have questions about this security warning or need to have it translated and you have an active technical support contract, please call 1-888-OPENLOGIC or email us at support@openlogic.com.

CVE Identifier: CVE-2009-2477
Severity: Critical