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Microsoft PowerPoint PPT 4.0 Importer Multiple Stack Buffer Overflow Vulnerabilities

12.05.09

BACKGROUND

Microsoft PowerPoint is an application used for constructing presentations, and comes with the Microsoft Office suite. For more information, see the vendor's site found at the following link.

http://office.microsoft.com/en-us/powerpoint/default.aspx

DESCRIPTION

Remote exploitation of multiple stack-based buffer overflow vulnerabilities in Microsoft Corp.'s PowerPoint could allow an attacker to execute arbitrary code with the privileges of the current user.

The vulnerabilities exist within the importer for PowerPoint 4.0 format files. This functionality is contained within the PP4X32.DLL.

The first vulnerability occurs when reading in a record header from the file. Due to an incorrect buffer size calculation, it is possible to overflow a stack-based buffer. Proper exploitation of this eventually leads to control of the instruction pointer register, allowing for the execution of arbitrary code.

The second vulnerability occurs when reading in record data from the file. An integer is taken from the file, and used to control the number of bytes to copy into a fixed size stack buffer. This leads to a trivially exploitable stack-based buffer overflow.

ANALYSIS

Exploitation of these vulnerabilities results in the execution of arbitrary code with the privileges of the user opening the file. To exploit these vulnerabilities, an attacker needs to convince a user to open a malicious file. After opening the file, no further interaction is needed to trigger the vulnerability.

Since the vulnerabilities are stack-based buffer overflows, and it is possible to overwrite SEH handlers or a frame pointer stored on the stack, exploitation is relatively simple.

DETECTION

iDefense has confirmed the existence of these vulnerabilities in the following versions of PowerPoint:

PowerPoint 2000 SP3

PowerPoint XP SP3

PowerPoint 2003 SP2 and SP3 contain the vulnerable code, but by default are unable to open PPT95 format files. This is due to the Office 2003 SP2/SP3 File Block Policy, which limits the file formats that Office applications will open without special permissions. If the targeted user has disabled the File Block Policy settings in PowerPoint 2003 SP3, then they are vulnerable. However, this is a non-default configuration. More on this policy can be found at the following URL.

http://support.microsoft.com/kb/938810

Office 2007 and Office 2007 SP1 are not vulnerable to these issues.

WORKAROUND

Use the cacls program to deny access to the DLL containing the vulnerable code, PP4X32.DLL. This will prevent the vulnerable DLL from loading in PowerPoint, which will also prevent users from importing PowerPoint 4.0 files. If Office 2003 SP3 is being used, then the default behavior is to block the opening of PowerPoint 4.0 files. If the default behavior has been changed, restoring it is an effective workaround.

VENDOR RESPONSE

Microsoft has released a patch which addresses this issue. For more information, consult their advisory at the following URL:

http://www.microsoft.com/technet/security/Bulletin/MS09-017.mspx

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2009-0220 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

DISCLOSURE TIMELINE

08/29/2008 - Initial Contact
08/29/2008 - Initial Response
08/29/2008 - PoC Requested
09/02/2008 - PoC Requested
09/03/2008 - PoC Sent
09/04/2008 - Vendor assigned case number
12/11/2008 - Status update received - no estimated release date
05/12/2009 - Coordinated Public Disclosure

CREDIT

This vulnerability was reported to iDefense by Marsu.

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LEGAL NOTICES

Copyright © 2009 Verisign, Inc.

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