iDefense Security Advisory 09.19.07: Multiple Vendor ImageMagick Off-By-One Vulnerability
- From: iDefense Labs <labs-no-reply@xxxxxxxxxxxx>
- Date: Fri, 21 Sep 2007 15:25:37 -0400
Multiple Vendor ImageMagick Off-By-One Vulnerability
iDefense Security Advisory 09.19.07
Sep 19, 2007
ImageMagick is a suite of image manipulation tools (animate, composite,
conjure, convert, display, identify, import, mogrify and montage) that
are sometimes used by other applications for processing image files.
For more information about ImageMagick, visit the vendor's site at the
Remote exploitation of an off-by-one vulnerability in ImageMagick, as
included in various vendors' operating system distributions, allows
attackers to execute arbitrary code.
This vulnerability specifically exists in the ReadBlobString() function
in magick/blob.c as shown below.
3110 for (i=0; i < (long) MaxTextExtent; i++)
3119 string[i]=(char) (*p);
3120 if ((string[i] == '\n') || (string[i] == '\r'))
The variable "string" is a character array of length "MaxTextExtent". An
off-by-one buffer overflow will occur on line 3123 when "i" is exactly
"MaxTextExtent". This function is called from several image file
processing routines. Most of the buffers involved are stack based,
although some are on the heap.
Exploitation of this vulnerability allows an attacker to execute
arbitrary code in the context of the user.
One way of exploiting this vulnerability is to persuade a targeted user
to open a malicious image file with a program that utilizes the
As the tools that are part of ImageMagick are sometimes used as helper
tools by other applications, this user may be the same as the web
server user. This scenario is somewhat more severe than the previously
described attack vector since the image processing can occur
Exploitation in stack-based scenarios depends on the stack layout, which
depends on the compiler and compiler options used to build the library.
iDefense Labs confirmed that ImageMagick version 6.3.4 is vulnerable. It
is suspected that other versions of ImageMagick are also vulnerable.
iDefense is unaware of any effective workaround for this vulnerability.
VI. VENDOR RESPONSE
The ImageMagick maintainers have addressed this vulnerability with the
release of version 6.3.5-9. More information is available from the
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-4987 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org/), which standardizes names for
VIII. DISCLOSURE TIMELINE
09/04/2007 Initial vendor notification
09/05/2007 Initial vendor response
09/19/2007 Coordinated public disclosure
This vulnerability was reported to iDefense by regenrecht.
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X. LEGAL NOTICES
Copyright © 2007 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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