Firefox 3.5 Security Bug in JavaScript JIT-compiler
A bug discovered last week in Firefox 3.5’s Just-in-time (JIT) JavaScript compiler was disclosed publicly yesterday. It is a critical vulnerability that can be used to execute malicious code.
Impact
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:
Enter about:config in the browser’s location bar.
Type jit in the Filter box at the top of the config editor.
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:
Enter about:config in the browser’s location bar.
Type jit in the Filter box at the top of the config editor.
Double-click the line containing javascript.options.jit.content setting the value to true.
Alternatively, users can disable the JIT by running Firefox 3,5 in Safe Mode. Windows users can do so by selecting Mozilla Firefox (Safe Mode) from the Mozilla Firefox folder.
Derzeit ungepatchte kritische Sicherheitslücke im Mozilla Firefox 3.5 Browser
JIT (JavaScript Just-in-Time-Compiler) in Firefox 3.5 sollte bis zum erscheinen eines updates für den Webbrowser Firefox 3.5 deaktiviert werden!
In der Adresszeile des Firefox-Browsers die URL “about:config” aufrufen und die Option javascript.options.jit.content auf “false” setzen.
Nach der Umkonfiguration ist man zwar erstmal auf der sicheren Seite, allerdings laufen nun JavaScripte erheblich langsamer.
Sobald ein Update verfügbar und installiert ist, stellt man den Wert einfach wieder auf “true”.
Unter Windows kann man Firefox auch alternativ im Safe Mode starten, dann wird JIT automatisch deaktiviert.
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