Microsoft Windows Graphics Device Interface Integer Overflow Vulnerability (MS08-071)
11 Dec. 2008
Summary
Microsoft Windows graphics device interface (GDI) enables applications to use graphics and formatted text on both the video display and the printer. Remote exploitation of an integer overflow vulnerability in multiple versions of Microsoft Corp.'s Windows operating system could allow an attacker to execute arbitrary code with the privileges of the current user.
Vulnerable Systems:
* gdi32.dll file version 5.1.2600.3316, as included in fully patched Windows XP Service Pack 2 as of May 2008
This vulnerability exists in the way GDI handles integer math. An integer overflow could occur while calculating the a buffer length, which results in an undersized heap buffer being allocated. This buffer is then overflowed with data from the input image file.
Analysis:
Exploitation allows an attacker to execute arbitrary code with the privileges of the current user. Exploitation would require convincing a targeted user to view a specially crafted image file. An attacker could host this file on a Web server, attach the file to an e-mail or embedded the file in an Office document.
This vulnerability also can be triggered through e-mail. If the e-mail client can automatically display images embedded in the e-mail, the user only needs to open the e-mail to trigger the vulnerability. Currently an EMF file is used as a test attack vector. Outlook and Outlook Express will automatically display EMF images and trigger the vulnerability. Lotus Notes and Thunderbird do not display EMF images in e-mail directly, but the vulnerability still can be triggered when opening or viewing the EMF attachment.
Workaround:
Turning off metafile processing by modifying the registry mitigates this threat. Under registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\GRE_Initialize create a DWORD entry "DisableMetaFiles" and set it to 1.
Note 1: This does not affect processes that are already running, so you might need to log off and log on again or restart the computer after making the change. Note 2: It only blocks one attack vector through Windows metafile. It is possibly to exploit this vulnerability through other attack vectors.
Impact of Workaround: components relying on metafile processing might not work properly, such as printing.
Viewing e-mail in plain text format mitigates e-mail-based attack.
Vendor response:
"The vulnerability could allow remote code execution if a user opens a specially crafted WMF image file. An attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts."
