And deep in IE, a creature was stirring…

Bug in the Rug

eEye security researcher Derek Soeder was moved to verse after analysing a complicated - and not particularly devastating - heap corruption vulnerability involving the way Windows handles PNG image format files.

An advisory by eEye begins thus:

Twas the night before Christmas, and deep in IE
A creature was stirring, a vulnerability
MS02-066 was posted on the website with care
In hopes that Team eEye would not see it there

But the engineers weren't nestled all snug in their beds,
No, PNG images danced in their heads
And Riley at his computer, with Drew's and my backing
Had just settled down for a little PNG cracking

When rendering an image, we saw IE shatter
And with just a glance we knew what was the matter
Away into SoftICE we flew in a flash
Tore open the core dumps, and threw RFC 1951 in the trash

The bug in the thick of the poorly-written code
Caused an AV exception when the image tried to load
Then what in our wondering eyes should we see
But our data overwriting all of heap memory

With heap management structures all hijacked so quick
We knew in a moment we could exploit this $#!%
More rapid than eagles our malicious pic came --
The hardest part of this exploit was choosing its name

As well as noting various unpatched versions of IE and Windows as potentially vulnerable to the bug, eEye notes BackOffice 4.5 is flawed for the same reason.

Although the vulnerability discussed in eEye's advisory might possibly be exploited to execute code when the malicious PNG image is viewed, the risk is not too serious.

As eEye notes "exploitation may become extremely difficult and in some cases unreliable", because of Windows memory management system protection features.

Also the flaw can be patched using either Internet Explorer 6 Service Pack 1 or by applying a separate security fixfrom MS, highlighted in eEye's not so terse verse. ®

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