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Date: Wed, 15 Apr 2009 15:25:53 -0400 From: iDefense Labs <labs-no-reply@...fense.com> To: bugtraq@...urityfocus.com, vulnwatch@...nwatch.org, full-disclosure@...ts.grok.org.uk Subject: iDefense Security Advisory 04.15.09: Microsoft WordPad Word97 Converter Stack Buffer Overflow Vulnerability -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 iDefense Security Advisory 04.14.09 http://labs.idefense.com/intelligence/vulnerabilities/ Apr 14, 2009 I. BACKGROUND WordPad is a word processing application included with Microsoft Windows. The Word97 converter is used to convert Word97 format documents into RTF format used by WordPad, and is present in all current versions of WordPad except Vista and Server 2008. II. DESCRIPTION Remote exploitation of a stack buffer overflow vulnerability in Microsoft Corp.'s WordPad could allow an attacker to execute arbitrary code with the privileges of the current user. The vulnerability occurs when parsing the content of a Word97 format file. When reading in the data, the code uses a 32-bit integer from the file to check a buffer length while using the lower 16-bit value to do the actual copy. This results in a stack buffer overflow. This stack buffer is overwritten with data from the file. III. ANALYSIS Exploitation of this vulnerability results in the execution of arbitrary code with the privileges of the user opening the file. To exploit this vulnerability, an attacker needs to convince a user to open a malicious file. Usually, WordPad is associated with the .DOC file extension unless Microsoft Word is installed. However, by renaming the .doc file to a .wri extension, it is possible to make WordPad open the file simply by double clicking it regardless of Microsoft Word being installed or not. IV. DETECTION iDefense has confirmed the existence of this vulnerability in Wordpad on Windows 2000 SP4. Windows XP SP3 is not affected. Vista and Server 2008 are not affected as they no longer contain the Word97 converter. V. WORKAROUND It is possible to disable access to the converter by changing the ACLs on the file. This can be accomplished as follows, depending on the version of Windows being used: echo y| cacls "%ProgramFiles%\Common Files\Microsoft Shared\TextConv\mswrd832.cnv" /E /P everyone:N echo y| cacls "%ProgramFiles(x86)%\Common Files\Microsoft Shared\TextConv\mswrd832.cnv" /E /P everyone:N echo y| cacls "%ProgramFiles%\Windows NT\Accessories\mswrd8.wpc" /E /P everyone:N echo y| cacls "%ProgramFiles%\Windows NT\Accessories\mswrd864.wpc" /E /P everyone:N echo y| cacls "%ProgramFiles(x86)%\Windows NT\Accessories\mswrd8.wpc" /E /P everyone:N VI. VENDOR RESPONSE Microsoft has released a patch which addresses this issue. This patch removes the vulnerability by changing the way that the WordPad Text Converters handle opening specially crafted Word 97 files. For more information, consult their advisory at the following URL: http://www.microsoft.com/technet/security/bulletin/MS09-010.mspx VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2009-0235 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 12/19/2008 - Initial Contact 12/31/2008 - PoC Request 01/06/2009 - PoC Sent 01/07/2009 - PoC Rcpt. ACK 02/19/2009 - Vendor Status Update 03/31/2009 - CVE Assigned 04/14/2009 - Coordinated Public Disclosure IX. CREDIT This vulnerability was discovered by Jun Mao and 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@...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. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFJ5jS/bjs6HoxIfBkRAoOOAKD+Qy2PvVo8UmlI+Z2C6e/3IfqqZgCeOaae x/hWVktm6YBYbTsACWMdifM= =Feo2 -----END PGP SIGNATURE----- _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
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