Public Vulnerability Reports

Multiple Vendor ImageMagick .psd Image File Decode Heap Overflow Vulnerability

01.17.05

BACKGROUND

ImageMagick provides a variety of graphics image-handling libraries and
capabilities. These libraries are widely used and are shipped by default
on most Unix and Linux distributions. These libraries are commonly
installed by default on computers where any other graphical image viewer
or X Desktop environment is installed (such as Gnome or KDE).

More information is available at the following site:

   http://www.imagemagick.org

DESCRIPTION

Remote exploitation of a buffer overflow vulnerability in The
ImageMagick's Project's ImageMagick PSD image-decoding module could
allow an attacker to execute arbitrary code.

A heap overflow exists within ImageMagick, specifically in the decoding
of Photoshop Document (PSD) files. The vulnerable code follows:

ImageMagick-6.1.0/coders/psd.c

for (j=0; j < (long) layer_info[i].channels; j++) 
{
  layer_info[i].channel_info[j].type=(short)ReadBlobMSBShort(image);
  layer_info[i].channel_info[j].size=ReadBlobMSBLong(image);
  [...]
}

The array channel_info is only 24 elements large, and the loop variable,
"j", is bounded by a user-supplied value from the image file, thus
allowing a heap overflow to occur when more than 24 layers are
specified. If heap structures are overflowed in a controlled way,
execution of arbitrary code is possible.

ANALYSIS

Exploitation may allow attackers to run arbitrary code on a victim's
computer if the victim opens a specially formatted image. Such images
could be delivered by e-mail or HTML, in some cases, and would likely
not raise suspicion on the victim's part. Exploitation is also possible
when a web-based application uses ImageMagick to process user-uploaded
image files.

DETECTION

iDEFENSE has confirmed this vulnerability in ImageMagick 6.1.0 and
ImageMagick 6.1.7. Earlier versions are also suspected vulnerable.

The following vendors may include vulnerable ImageMagick packages:
 
   The Debian Project
   MandrakeSoft
   Red Hat, Inc.

WORKAROUND

Do not open files from untrusted sources. Do not allow untrusted sources
to process images using your web application.

VENDOR RESPONSE

This vulnerability is addressed in ImageMagick 6.1.8-8, available for
download at:

   http://www.imagemagick.org/www/download.html

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2005-0005 to these issues. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

DISCLOSURE TIMELINE

12/21/2004   Initial vendor notification
01/14/2004   Initial vendor response
01/17/2005   Public disclosure

CREDIT

Andrei Nigmatulin is credited with this discovery.

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LEGAL NOTICES

Copyright © 2004 Verisign, 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,
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