iDefense Security Advisory 08.12.08 http://labs.idefense.com/intelligence/vulnerabilities/ Aug 12, 2008 I. BACKGROUND Microsoft Excel is the spreadsheet application that is 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 an invalid array indexing vulnerability in Microsoft Corp.'s Excel could allows attackers to execute arbitrary code with the privileges of the current user. This issue exists in the handling of "FORMAT" records within an Excel spreadsheet (XLS). By crafting a spreadsheet with an out-of-bounds array index, attackers are able to cause Excel to write a byte to arbitrary locations in stack memory. 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 on web sites from opening automatically. 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 SP-3 fully patched as of March 2008. Other versions may also be affected. V. WORKAROUND iDefense is currently unaware of any effective workaround for this issue. VI. VENDOR RESPONSE Microsoft has officially addressed this vulnerability with Security Bulletin MS08-044. For more information, consult their bulletin at the following URL. http://www.microsoft.com/technet/security/bulletin/ms08-044.mspx VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2008-3005 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 03/27/2008 Initial vendor notification 03/28/2008 Initial vendor response 08/12/2008 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@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.
