Software Engineering Institute

The JavaScript programming language uses a method of memory management known as automatic garbage collection. A vulnerability has been discovered in the way that the JavaScript engine included with Mozilla and derived programs handles the process of garbage collection. According to Mozilla Foundation Security Advisory 2006-10:

Igor Bukanov has audited the JavaScript engine for routines that use temporary variables not protected against garbage-collection. If malicious content could cause garbage-collection to run during the lifetime of these temporaries then the original routine would end up operating on freed memory.

The risk appears remote, but this type of memory corruption could potentially be used by an attacker to run arbitrary code including the installation of malware.

Note: Thunderbird shares the JavaScript engine with Firefox and could be vulnerable if JavaScript were to be enabled in mail. This is not the default setting and we strongly discourage users from running JavaScript in mail.

A remote attacker may be able to run code of their choosing on an affected system. The attacker-supplied code would be executed with the permissions of the user running the vulnerable program.

Upgrade

The Mozilla Foundation has published Mozilla Foundation Security Advisory 2006-10 in response to this issue. Users are encouraged to review this advisory and upgrade to the fixed versions of the products it describes.

Workarounds

Users, particularly those who are unable to upgrade to a fixed version of the software, are encouraged to disable JavaScript in the affected program.