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Multiple Vendor ART File Heap Corruption Vulnerability

06.13.06

BACKGROUND

America Online, as well as 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 subsequently purchased the company to secure the rights
to it in 1996. 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.

DESCRIPTION

Remote exploitation of a heap corruption vulnerability America Online's
ART file handling libraries, as included in various vendors' software,
allows attackers to execute arbitrary code.

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
exploitation.

ANALYSIS

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.

DETECTION

iDefense has confirmed that multiple vendors' products are affected.
America Online has reported that all AOL client versions are affected.

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.

WORKAROUND

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:

C:\windows\system32\jgpl400.dll
C:\windows\system32\jgdw400.dll
C:\windows\system32\jgaw400.dll
C:\windows\system32\jgsd400.dll
C:\windows\system32\jgmd400.dll
C:\windows\system32\jgsh400.dll

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

VENDOR RESPONSE

America Online has suggested the following remediation:

• AOL Members who are currently using AOL 9.0 need only log in to
the AOL service and a fix will be seamlessly applied to their
system.
• AOL Members who are currently using an earlier version of the AOL
client are recommended to upgrade to AOL 9.0 Security Edition
The Microsoft security advisory and appropriate patches are available at:

http://www.microsoft.com/technet/security/Bulletin/MS06-022.mspx

CVE INFORMATION

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.

DISCLOSURE TIMELINE

02/07/2006 Initial vendor notification
02/07/2006 Initial vendor response
06/13/2006 Coordinated public disclosure - Microsoft
08/29/2006 Coordinated public disclosure - America Online

CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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LEGAL NOTICES

Copyright © 2006 Verisign, Inc.

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without the express
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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.