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Microsoft Internet Explorer ART File Heap Corruption Vulnerability
iDefense Security Advisory 06.13.06: Microsoft Internet Explorer ART File Heap Corruption Vulnerability
iDefense Security Advisory 06.13.06: Microsoft Internet Explorer ART File Heap Corruption Vulnerability

Microsoft Internet Explorer ART File Heap Corruption Vulnerability

iDefense Security Advisory 06.13.06
June 13, 2006


Internet Explorer is the web browser included in Microsoft Corp.'s
Windows products.


Remote exploitation of a heap corruption vulnerability in Microsoft
Corp.'s Internet Explorer allows attackers to execute arbitrary code.

Internet Explorer supports Johnson-Grace compressed images, or .art
files. Johnson-Grace developed this technology in 1991. In 1994,
American Online Inc. began using the technology and, in 1996, purchased
the company to secure rights to it. It is now licensed to Microsoft for
usage in Internet Explorer by way of the jgdw400.dll dynamically linked
library, which is copyrighted by AOL.

The vulnerability specifically exists due to improper parsing of a
malformed .art file during rendering. With a carefully crafted .art
file, it is possible to overwrite portions of the heap with static
values from a file independent table in memory. Although this typically
would be somewhat limiting from an exploitation standpoint, in this case
an attacker can utilize large images or JavaScript to fill the heap so
that these static values reliably point into controlled regions. Because
there are an abundance of function pointers on the heap that an attacker
may smash, heap integrity checks are not effective in preventing


Successful exploitation of this vulnerability allows attackers to
execute arbitrary code with the privileges of the currently logged-on
user. iDefense Labs analysis has shown that exploitation can be as
reliable as 75 percent with the current exploitation method. Upon failed
exploitation attempts, the system may become slow or unresponsive due to
the method employed by the exploit to fill memory in order to facilitate
an exploitable memory state.

It should be noted that hardware data execution prevention (DEP) will
prevent exploitation from occurring by the iDefense Labs-maintained
exploit code. This is a result of the payload executing on the heap,
which is marked writable and thus not executable.

It should also be noted that the file does NOT need to have an .art
extension to be rendered by the vulnerable library. Any extension can be
used, provided the image is loaded via an IMG SRC tag in an HTML
document in Internet Explorer.


iDefense has confirmed that the following Microsoft products are
affected in default configurations:
    Windows XP
    Windows XP SP1
    Windows XP SP2
    Windows 2003
    Windows 2003 SP1
iDefense has confirmed that the following Microsoft products are
affected when recommended Windows feature updates have been installed:

  Windows 2000 SP4
To determine if a Windows 2000 system is affected, check for the
existence of the file jgdw400.dll on the system. If the file exists, the
system is affected.


iDefense has developed the following workaround, which has not
demonstrated any impairment to the system in testing. However, as this
is not a vendor-supplied workaround, it should be tested thoroughly
before being applied to a production environment. Remove the following
dynamically linked libraries from:


This will effectively disable the viewing of all .ART files on the system.


The vendor security advisory and appropriate patches are available at:



The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2006-2378 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org), which standardizes names for 
security problems.


02/07/2006  Initial vendor notification
02/07/2006  Initial vendor response
06/13/2006  Coordinated public disclosure


The discoverer of this vulnerability wishes to remain anonymous.

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Copyright =A9 2006 iDefense, Inc.

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.

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