Message-ID: <4642243F.6020904@idefense.com>
Date: Wed, 09 May 2007 15:42:55 -0400
From: iDefense Labs <labs-no-reply@...fense.com>
To: vulnwatch@...nwatch.org, full-disclosure@...ts.grok.org.uk,
	bugtraq@...urityfocus.com
Subject: iDefense Security Advisory 05.08.07: Microsoft Word RTF File Parsing
 Heap Corruption Vulnerability

Microsoft Word RTF File Parsing Heap Corruption Vulnerability

iDefense Security Advisory 05.08.07
http://labs.idefense.com/intelligence/vulnerabilities/
May 08, 2007

I. BACKGROUND

Microsoft Word is a word processing application from Microsoft Office.
Rich Text Format (RTF) is a document file format developed by Microsoft
for cross-platform document interchange. For more information about
Microsoft Word, see following web site.

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

II. DESCRIPTION

Remote exploitation of a heap corruption vulnerability in Microsoft
Corp.'s Word could allow attackers to execute arbitrary code under the
privileges of the target user.

This vulnerability specifically exists in the handling of property
strings of certain control words in an RTF document. In certain
circumstances, these property strings can be written into a memory
region which has already been deallocated and heap corruption can
occur.

III. ANALYSIS

Successful exploitation of this vulnerability allows remote attackers to
execute arbitrary code on the affected host within the context of the
user who opened the malicious RTF document with Microsoft Word.

Microsoft Word, if installed, will be the default application for
opening RTF files. If Microsoft Word is not installed, WordPad will be
the default application for opening RTF files, which is not vulnerable
to this attack.

Exploitation requires that the user opens a specially crafted RTF
document with a vulnerable application. The most likely exploitation
vector involves convincing a user to open an RTF document sent to them
via e-mail, or linked on a website.

Enabling hardware Data Execution Prevention (DEP) on systems that
support it (i.e., Windows XP SP2 and Windows Server 2003 SP1 on
hardware with AMD processors supporting NX or Intel processors
supporting XD) mitigates this vulnerability. While it may be possible
for attackers to bypass this protection, it can prevent some typical
exploitation methods.

IV. DETECTION

iDefense has confirmed that winword.exe file version 11.0.8106.0, as
included with a fully patched Microsoft Word 2003 SP2, is vulnerable.
Previous versions of Microsoft Word are also likely to be affected.

V. WORKAROUND

Since WordPad.exe is not affected by this vulnerability, changing the
default association for RTF files to use WordPad is considered an
effective workaround. However, simply changing the file extension can
bypass this workaround.

VI. VENDOR RESPONSE

Microsoft has addressed this vulnerability within MS07-024. For more
information, consult their bulletin at the following URL.

http://www.microsoft.com/technet/security/Bulletin/MS07-024.mspx

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-1202 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

02/27/2007  Initial vendor notification
02/27/2007  Initial vendor response
05/08/2007  Coordinated public disclosure

IX. CREDIT

This vulnerability was reported to iDefense by an anonymous researcher.
Further analysis was performed by Jun Mao (iDefense Labs).

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X. LEGAL NOTICES

Copyright © 2007 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@...fense.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.

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