iDefense Security Advisory 08.12.08: Microsoft Office BMP Input Filter Heap Overflow Vulnerability
iDefense Security Advisory 08.12.08
http://labs.idefense.com/intelligence/vulnerabilities/
Aug 12, 2008
I. BACKGROUND
Microsoft Office contains a number of input filters. These input filters
allow transparent conversion from external types into a form that the
Office applications can use. More information on import filters in
Microsoft Office 2002 is available at the following URL.
http://support.microsoft.com/?scid=kb;en-us;290362
II. DESCRIPTION
Remote exploitation of a heap buffer overflow vulnerability in the
"BMPIMP32.FLT" filter module, as distributed with Microsoft Office,
allows attackers to execute arbitrary code.
The vulnerability specifically exists in the handling of Windows Bitmap
(BMP) image files with malformed headers. By specifying a very large
number of colors in the header, it is possible to cause controllable
heap corruption, which can be leveraged to execute arbitrary code.
III. ANALYSIS
Exploitation could allow attackers to execute arbitrary code on the
targeted host under the security context of the current logged in user.
Successful exploitation would require the attacker to entice his or her
victim into opening a specially crafted BMP image with a vulnerable
version of Office.
IV. DETECTION
iDefense confirmed that the "BMPIMP32.FLT" module installed with
Microsoft Office XP SP3, including all patches as of May 24, 2006, is
vulnerable. Other versions may also be vulnerable.
This vulnerability does not affect Microsoft Office 2003 as this filter
is not installed or required.
V. WORKAROUND
This workaround replaces the affected filter with an empty file.
Creating this file prevents Office from offering to reinstall the
affected component.
1. Close all running applications.
2. Open the folder "C:\Program Files\Common Files\Microsoft
Shared\Grphflt".
3. Rename the file "BMPIMP32.FLT" to "BMPIMP.FLT.disabled".
4. Create an empty file in this directory with the name
"BMPIMP32.FLT". (Open Notepad, go to this directory and choose File,
Save..., type "BMPIMP32.FLT" including the quotes and click Save.
In testing on Windows 2000 with Office XP SP3 installed, this workaround
did not adversely impact functionality. BMP format image files can still
be imported into Word, but the operations that can be performed on them
may be impacted.
VI. VENDOR RESPONSE
Microsoft has officially addressed this vulnerability with Security
Bulletin MS08-044. For more information, consult their bulletin at the
following URL.
http://www.microsoft.com/technet/security/bulletin/ms08-044.mspx
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2008-3020 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
09/11/2006 Initial vendor notification
09/11/2006 Initial vendor response
08/12/2008 Coordinated public disclosure
IX. CREDIT
The discoverer of this vulnerability wishes to remain anonymous.
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at the time of publishing based on currently available information. Use
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