iDefense Security Advisory 03.09.10 http://labs.idefense.com/intelligence/vulnerabilities/ Mar 09, 2010 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 heap overflow vulnerability in Microsoft Corp.'s Excel could allow an attacker to execute arbitrary code with the privileges of the current user. This vulnerability occurs when parsing an MDXTUPLE record inside of the Excel Workbook globals stream. This record is used to store metadata for external data connections in the workbook. The vulnerability occurs when a MDXTUPLE record is broken up into several records. This could allow an attacker to trigger a heap based buffer overflow by controlling both the allocation size of a heap buffer and the number of bytes copied into this buffer. 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. Attackers typically accomplish this by emailing a targeted user the file, or hosting the file on a Web page. Exploitation of this vulnerability is relatively simple. An attacker can control the size of the buffer allocated, the size of the overflow, and the content of the overflow. IV. DETECTION iDefense has confirmed the existence of this vulnerability in Excel versions 2007 SP0, SP1, and SP2. Previous versions do not appear to be affected as they do not support parsing the record that triggers the vulnerability. A full list of vulnerable Microsoft products can be found in Microsoft Security Bulletin MS10-017. V. WORKAROUND Microsoft suggested workarounds can be found in Microsoft Security Bulletin MS10-017. VI. VENDOR RESPONSE Microsoft Corp. has released a patch which addresses this issue. Information about downloadable vendor updates can be found by clicking on the URLs shown. http://www.microsoft.com/technet/security/bulletin/MS10-017.mspx VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2010-0260 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 09/25/2009 Initial Vendor Notification 09/25/2009 Initial Vendor Reply 03/09/2010 Coordinated Public Disclosure 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 © 2010 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.
