iDefense Security Advisory 08.11.09
http://labs.idefense.com/intelligence/vulnerabilities/
Aug 11, 2009

I. BACKGROUND

Office Web Components is a group of ActiveX controls that can be used to
view and edit Microsoft Office files such as spreadsheets and charts. It
is commonly used to allow a user to edit a spreadsheet in the browser.
The controls are installed with a default installation of Microsoft
Office. More information can be found at the vendor's website at the
following address.

http://www.microsoft.com/downloads/details.aspx?FamilyID=982B0359-0A86-4FB2-A7EE-5F3A499515DD

II. DESCRIPTION

Remote exploitation of a stack based buffer overflow vulnerability in
Microsoft Corp.'s Office Web Components 2000 could allow an attacker to
execute arbitrary code with the privileges of the logged on user.

When instantiating a Spreadsheet object, it is possible to pass the
object a parameter that refers to an Excel file that will be retrieved
and then loaded. By using a long string for the parameter, it is
possible to case a stack based buffer overflow.

III. ANALYSIS

Exploitation results in the execution of arbitrary code with the
privileges of the logged-on user. Exploitation would require that an
attacker hosts a maliciously crafted page on a Web site and entice
users to visit the site. No further action is needed other than
following a link to a malicious Web page.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in Microsoft
Office XP Service Pack 3. Microsoft reports that the following products
are affected:

  Microsoft Office XP Service Pack 3
  Microsoft Office 2000 Web Components SP3
  Microsoft Office XP Web Components SP3
  Microsoft BizTalk Server 2002
  Visual Studio .NET 2003 Service Pack 1

V. WORKAROUND

Setting the kill bit for the following CLSIDs will mitigate the threat
from web based attacks conducted through Internet Explorer. The CLSID
for the vulnerable control is:

  0002E512-0000-0000-C000-000000000046

VI. 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/MS09-043.mspx

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2009-1534 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

03/17/2008  Initial vendor notification
03/17/2008  Initial vendor response
03/17/2008  PoC requested
03/17/2008  Poc sent
04/18/2008  Status update request sent
05/28/2008  Status update request sent
07/03/2008  Status update received, new case manager assigned
06/26/2009  Status update received, new case manager assigned
06/26/2009  Bulletin release scheduled for July
07/09/2009  Status update received, bulletin delayed
08/11/2009  Public disclosure by Microsoft

IX. CREDIT

This vulnerability was discovered by Sean Larsson, iDefense Labs.

Get paid for vulnerability research
http://labs.idefense.com/methodology/vulnerability/vcp.php

Free tools, research and upcoming events
http://labs.idefense.com/

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@idefense.com 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.