bugtraq - New IE crash: CSS + HTML

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Date: Fri, 03 Oct 2003 17:43:13 +1200 (NZST)
From: arachnid__notdot_net@...a.net.nz
To: bugtraq@...urityfocus.com
Subject: New IE crash: CSS + HTML

While designing a page today, I stumbled across a combination of HTML and CSS
that causes IE (6.0.2600.0000 on 2k v5.00.2195 and 6.0.3790 on 2k3 server
v5.2.3790 are the only versions tested so far) to crash with a GPF. After a
little work, I distilled the required code down to this:

-----------------------------------------
<html>
<body>
<style type="text/css">
	#three {
		position: absolute;
	}
	#one #two {
		position: absolute;
	}
</style>
<div id="one">
	In 'one'
	<span id="two">
	In 'two'
</div>
<div id="three">
	In 'three'
</div>
</body>
-----------------------------------------

A bit of experimentation revealed the following:
The tag with id "one" can be any tag that is 'display: block' by default.
The tag with id "two" can be any tag that is 'display: inline' by default.
The tag with id "three" can be any tag at all, including non container tags such
as img.
The tag with id "two" _must_ be left unclosed.
The selector must be "#one #two", simply selecting on #two does not work.

I'll be the first to admit that this is a bit obscure (though I came across it
by accident) - it seems to have something to do with opening an absolutely
positioned block tag after an absolutely positioned inline tag wasn't closed
properly, but is more complicated than that.
In windows 2000, it also crashed explorer when I clicked on the file in in a
file dialog (due to the auto-preview).

A brief look at a debugger on the crashed IE instance reveals that the address
it crashes at is a RET instruction.

I leave it up to people with more talent than I to refine when it occurs and why ;).

-Nick Johnson