I. 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.
II. 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.
III. 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.
IV. 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.
V. 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.
VI. 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
VII. 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.
VIII. 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
IX. CREDIT
The discoverer of this vulnerability wishes to remain anonymous.
Get paid for vulnerability research
http://www.idefense.com/poi/teams/vcp.jsp
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http://labs.idefense.com
X. LEGAL NOTICES
Copyright © 2006 iDefense, Inc.
Permission is granted for the redistribution of this
alert
electronically. It may not be edited in
any way without the express
written consent of iDefense. If you wish to
reprint the whole or
any
part of this alert in any other medium other than electronically,
please
email customerservice@idefense.com
for
permission.
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.
