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Mozilla XPCOM Library Race Condition
From: GulfTech Security Research <security () gulftech org>
Date: Thu, 21 Jul 2005 12:28:20 -0500

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# GulfTech Security Research          July 21st, 2005
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# Vendor  : Mozilla
# URL     : http://www.mozilla.org/projects/xpcom/
# Version : Not Available
# Risk    : Race Condition
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Description:
xpcom, or cross platform component object model is a framework for
writing cross-platform, modular software. The xpcom library is used
in many applications including a majority of the popular browsers
such as FireFox, NetScape, Mozilla, Galeon, etc. It seems that
there is a race condition of sorts in xpcom that makes it possible
for an attacker to crash a victims browser by having them view a
malformed html document. This issue is not believed to be exploitable
by the Mozilla dev team, and will likely be addressed in full at a
later date by the development team.



XPCOM Race Condition:
It is possible for an attacker to create a race condition that will
cause an access violation and result in a hard crash of the browser.
One way to trigger this issue is by taking a decent sized html file
and loading a dom call within some nested divs that will cause part
of the page currently being rendered to be deleted. If the page has
not loaded by the time the dom call is made then we can delete
objects that have yet to be referenced, which will result in a crash
as soon as the browser tries to reference the deleted object.

http://www.gulftech.org/wrecko.html

The above link is a simple proof of concept I wrote a few months ago
to show the developers how the issue could be used to cause a crash of
the affected web browser. Due to time constraints I have not got to look
into this issue very in depth, but it may be possible to use the race
condition described here in combination with other dom calls or javascript
to produce different results than those demonstrated in my proof of
concept html page.



Solution:
Mozilla have been aware of this issue for some months, and have fixed the
issue on trunk, but not on branch. The reason for this as stated by one of
the developers is "fixes for this stuff could easily cause regressions". I
did test this issue on the latest copy of the mozilla browser (Deer Park)
this morning though, and it seemed to NOT be vulnerable. However, firefox
and the like are still affected.



Related Info:
The original advisory can be found at the following location
http://www.gulftech.org/?node=research&article_id=00091-07212005



Credits:
James Bercegay of the GulfTech Security Research Team


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