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Mozilla Foundation Security Advisory 2006-48

Title: JavaScript new Function race condition
Impact: Critical
Announced: July 25, 2006
Reporter: H. D. Moore
Products: Firefox, Thunderbird, SeaMonkey

Fixed in: Firefox 1.5.0.5
  Thunderbird 1.5.0.5
  SeaMonkey 1.0.3

Description

H. D. Moore reported a testcase that was able to trigger a race condition where JavaScript garbage collection deleted a temporary variable still being used in the creation of a new Function object. The resulting use of a deleted object may be potentially exploitable to run native code provided by the attacker.

This vulnerability was introduced during Firefox 1.5 development, it does not affect Firefox 1.0 or Mozilla Suite 1.7

Thunderbird shares the browser engine with Firefox and would be vulnerable if JavaScript were to be enabled in mail. This is not the default setting and we strongly discourage users from enabling JavaScript in mail.

Workaround

Disable JavaScript until you can upgrade to a fixed version. Do not enable JavaScript in mail clients such as Thunderbird.

References