Security Services

Microsoft Excel Uninitialized Pointer Memory Corruption Vulnerability

12.04.16

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/

DESCRIPTION

Remote exploitation of a memory corruption vulnerability in Microsoft Corp.'s Excel, could allow attackers to execute arbitrary code with the privileges of the current user. Excel when processing a malformed file attempts to use a pointer which has never been initialized. This results in an exploitable situation.

ANALYSIS

Successful exploitation could allow an attacker to execute arbitrary code with the privileges of the user opening the file. The attacker can also cause a denial of service (DoS) condition. To exploit this vulnerability, the attacker must socially-engineer a user to open a specially crafted file. Attackers typically accomplish this by e-mailing a targeted user the file or hosting the file on a Web page. Note that attackers cannot exploit Office file format vulnerabilities in a drive-by manner; at a minimum, a targeted user must click an "open" dialog or choose to view an attachment. In this vulnerability, the attacker will also have to persuade the victim to click through the pop-up dialog box which Excel shows to the user when the user opens the exploit Excel file. When on the Windows platform, iDefense recommends configuring the affected application to use the exploitation mitigation methods that the Microsoft Corp. Enhanced Mitigation Experience Toolkit (EMET) tool provides. This will not prevent exploitation, but it will make it more complex on platforms that support data execution prevention (DEP) and address space layout randomization (ASLR). iDefense considers this vulnerability to be of MEDIUM-severity due to the possibility of arbitrary code execution, mitigated by the need for user interaction.

DETECTION

The following vendors include susceptible software within their respective software distributions:

  • Microsoft: excel 2010
  • WORKAROUND

    iDefense is unaware of any workaroundfor this vulnerability.

    VENDOR RESPONSE

    Microsoft has released a fix which addresses this issue. For more information, consult their advisory at the following URL:

    https://technet.microsoft.com/en-us/library/security/ms16-042/

    CVE INFORMATION

    The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2016-0136 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

    DISCLOSURE TIMELINE

    02/19/2016 Initial Vendor Notification
    02/19/2016 Initial Vendor Reply
    04/12/2016 Coordinated Public Disclosure

    CREDIT

    This vulnerability was reported to iDefense by Steven Seeley of Source Incite .

    Get paid for vulnerability research https://labs.idefense.com/vcpportal/login.html

    LEGAL NOTICES

    Copyright © 2016 Verisign, 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 Verisign. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please email customer service 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.