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Mozilla Foundation Security Advisory 2009-41

Title: Corrupt JIT state after deep return from native function
Impact: Critical
Announced: July 16, 2009
Reporter: zbyte
Products: Firefox 3.5

Fixed in: Firefox 3.5.1


Firefox user zbyte reported a crash that we determined could result in an exploitable memory corruption problem. In certain cases after a return from a native function, such as escape(), the Just-in-Time (JIT) compiler could get into a corrupt state. This could be exploited by an attacker to run arbitrary code such as installing malware.

We would like to thank community members Lucas Kruijswijk and Nochum Sossonko for isolating the problematic script from the original crashing site.

This vulnerability does not affect earlier versions of Firefox which do not support the JIT feature.


Users of Firefox 3.5 can avoid this vulnerability by disabling the Just-in-Time compiler as described in the Mozilla Security Blog. That workaround is not necessary in Firefox 3.5.1 and can be reverted.