-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 iDefense Security Advisory 12.09.08 http://labs.idefense.com/intelligence/vulnerabilities/ Dec 09, 2008 I. BACKGROUND Excel is the spreadsheet application included with Microsoft Corp.'s Office productivity software suite. More information is available at the following website: http://office.microsoft.com/excel/ II. DESCRIPTION Remote exploitation of a memory corruption vulnerability in Microsoft Corp.'s Excel spreadsheet could allow attackers to execute arbitrary code with the privileges of the current user. This issue exists in the handling of certain malformed object records within an Excel spreadsheet (XLS), allowing memory corruption to occur. This could lead to an exploitable situation. iDefense's proof of concept code can redirect the program execution flow to a user controllable address on Excel 2000 SP3, and crash on other versions of Excel, including Excel XP SP3, Excel 2003 SP3 and Excel 2007 SP1. III. ANALYSIS Exploitation allows an attacker to execute arbitrary code in the context of the currently logged-on user. To exploit this vulnerability, the attacker must persuade a user to open a specially crafted Excel (XLS) document. Likely attack vectors include sending the file as an e-mail attachment or linking to the file on a website. By default, systems with Office 2000 installed will open Office documents, including Excel spreadsheet files, from websites without prompting the user. This allows attackers to exploit this vulnerability without user interaction. Later versions of Office do not open these documents automatically unless the user has chosen this behavior. Using the Office Document Open Confirmation Tool for Office 2000 can prevent Office files from opening automatically from web sites. Use of this tool is highly recommended for users still using Office 2000. IV. DETECTION iDefense has confirmed the existence of this vulnerability with Office 2000 SP3 fully patched as of July 2008. V. WORKAROUND iDefense is currently unaware of any effective workaround for this issue, since the vulnerability exists in the core component of Excel. VI. VENDOR RESPONSE Microsoft Corp. 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/ms08-074.mspx VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2008-4265 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 07/21/2008 Initial Vendor Notification 07/22/2008 Initial Vendor Reply 07/24/2008 Additional Vendor Feedback 12/09/2008 Coordinated Public Disclosure IX. CREDIT The discoverer of this vulnerability wishes to remain anonymous. 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 © 2008 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. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFJQB6ebjs6HoxIfBkRAjKTAKD3meNs6BwgFJhQDoUlNy6qqa09ZQCdFLST XWdAq1pjchUyhLQ94ZfT2uE= =atK5 -----END PGP SIGNATURE-----