iDefense Security Advisory 05.12.09: Microsoft PowerPoint PPT95 Import Multiple Stack Buffer Overflow Vulnerabilities

[iDefense Labs <labs-no-reply@xxxxxxxxxxxx>]

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iDefense Security Advisory 05.12.09
http://labs.idefense.com/intelligence/vulnerabilities/
May 12, 2009

I. BACKGROUND

Microsoft PowerPoint is the presentation application that is included
with Microsoft Corp's Office productivity software suite. More
information is available at the following website.

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

II. 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 95 format
files. This functionality is contained within the PP7X32.DLL.

The first vulnerability occurs when reading data that describes a sound
object embedded in the file. A record length value is read in from the
file. This value is then used to control how many bytes are stored in a
fixed size stack buffer. There is no check performed to ensure that the
buffer can hold the number of bytes specified. This can lead to a stack
buffer overflow.

The second vulnerability occurs when reading in record name strings from
the file. A string from the file is copied into a fixed size stack
buffer without verifying that the destination buffer is large enough to
hold the string. This results in a stack buffer overflow.

III. 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 and function pointers stored on the
stack, exploitation is relatively simple.

IV. DETECTION

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

PowerPoint 2000 SP3

PowerPoint XP SP3

PowerPoint 2003 SP2 PowerPoint 2003 SP3 contains the vulnerable code,
but by default it is unable to open PPT95 format files. This is due to
the Office 2003 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.

V. WORKAROUND

Use the cacls program to deny access to the DLL containing the
vulnerable code, PP7X32.DLL. This will prevent the vulnerable DLL from
loading in PowerPoint, which will also prevent users from importing
PowerPoint 95 files. If Office 2003 SP3 is being used, then the default
behavior is to block the opening of PowerPoint 95 files. If the default
behavior has been changed, restoring it is an effective workaround.

VI. VENDOR RESPONSE

[Quoted vendor response if available. Otherwise include vendor fix
details.]

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2009-1128 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

06/16/2008  - Initial Contact
06/16/2008  - PoC Sent
06/17/2008  - Initial Response
06/18/2008  - Confirmation received - no estimated release date
07/22/2008  - Status Update Requested
07/23/2008  - Status Update Received - Update planned in November
12/11/2008  - Status Update Received - no estimated release date
02/19/2009  - Status Update Received - new case manager, estimated
release date 06/09/2009
04/23/2009  - Status Update - release on track
05/12/2009  - Coordinated Public Disclosure

IX. CREDIT

This vulnerability was reported to iDefense by Marsu.

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X. LEGAL NOTICES

Copyright © 2009 iDefense, Inc.

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without the express
written consent of iDefense. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically,
please e-mail customerservice@xxxxxxxxxxxx for permission.

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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