Microsoft Security Bulletin MS16-121 - Critical

Security Update for Microsoft Office (3194063)

Published: October 11, 2016 | Updated: October 12, 2016

Version: 1.1

Executive Summary

This security update resolves a vulnerability in Microsoft Office. An Office RTF remote code execution vulnerability exists in Microsoft Office software when the Office software fails to properly handle RTF files. An attacker who successfully exploited the vulnerabilities could run arbitrary code in the context of the current user.

The update addresses the vulnerability by changing the way Microsoft Office software handles RTF content.

For more information about the vulnerabilities, see the Affected Software and Vulnerability Severity Ratings section.

For more information about this update, see Microsoft Knowledge Base Article 3194063. 

Affected Software and Vulnerability Severity Ratings

The following software versions or editions are affected. Versions or editions that are not listed are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, see Microsoft Support Lifecycle.

The following severity ratings assume the potential maximum impact of the vulnerability. For information regarding the likelihood, within 30 days of this security bulletin's release, of the exploitability of the vulnerability in relation to its severity rating and security impact, please see the Exploitability Index in the October bulletin summary. 

Microsoft Office Software

^[1]This update is available via Windows Update.

*The Updates Replaced column shows only the latest update in a chain of superseded updates. For a comprehensive list of updates replaced, go to the Microsoft Update Catalog, search for the update KB number, and then view update details (updates replaced information is on the Package Details tab).

Microsoft Office Services and Web Apps

*The Updates Replaced column shows only the latest update in a chain of superseded updates. For a comprehensive list of updates replaced, go to the Microsoft Update Catalog, search for the update KB number, and then view update details (updates replaced information is on the Package Details tab).

Update FAQ

I have Microsoft Word 2010 installed. Why am I not being offered the 3118311 update?
The 3118311 update only applies to systems running specific configurations of Microsoft Office 2010. Some configurations will not be offered the update.

I am being offered this update for software that is not specifically indicated as being affected in the Affected Software and Vulnerability Severity Ratings table. Why am I being offered this update?
When updates address vulnerable code that exists in a component that is shared between multiple Microsoft Office products or shared between multiple versions of the same Microsoft Office product, the update is considered to be applicable to all supported products and versions that contain the vulnerable component.

For example, when an update applies to Microsoft Office 2007 products, only Microsoft Office 2007 may be specifically listed in the Affected Software table. However, the update could apply to Microsoft Word 2007, Microsoft Excel 2007, Microsoft Visio 2007, Microsoft Compatibility Pack, Microsoft Excel Viewer, or any other Microsoft Office 2007 product that is not specifically listed in the Affected Software table. Furthermore, when an update applies to Microsoft Office 2010 products, only Microsoft Office 2010 may be specifically listed in the Affected Software table. However, the update could apply to Microsoft Word 2010, Microsoft Excel 2010, Microsoft Visio 2010, Microsoft Visio Viewer, or any other Microsoft Office 2010 product that is not specifically listed in the Affected Software table.

For more information on this behavior and recommended actions, see Microsoft Knowledge Base Article 830335. For a list of Microsoft Office products that an update may apply to, refer to the Microsoft Knowledge Base Article associated with the specific update.

Vulnerability Information

Microsoft Office Memory Corruption Vulnerability

An Office RTF remote code execution vulnerability exists in Microsoft Office software when the Office software fails to properly handle RTF files. An attacker who successfully exploited the vulnerabilities could run arbitrary code in the context of the current user. If the current user is logged on with administrative user rights, an attacker could take control of the affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

Exploitation of the vulnerability requires that a user open a specially crafted file with an affected version of Microsoft Office software. In an email attack scenario an attacker could exploit the vulnerability by sending the specially crafted file to the user and convincing the user to open the file. In a web-based attack scenario an attacker could host a website (or leverage a compromised website that accepts or hosts user-provided content) that contains a specially crafted file that is designed to exploit the vulnerabilities. An attacker would have no way to force users to visit the website. Instead, an attacker would have to convince users to click a link, typically by way of an enticement in an email or Instant Messenger message, and then convince them to open the specially crafted file.

The update addresses the vulnerability by changing the way Microsoft Office software handles RTF content.

Microsoft received information about this vulnerability through coordinated vulnerability disclosure. Microsoft is aware of limited attacks that use this vulnerability in conjunction with other vulnerabilities to gain code execution.

The following table contains the link to the standard entry for the vulnerability in the Common Vulnerabilities and Exposures list:

Mitigating Factors

Microsoft has not identified any mitigating factors for these vulnerabilities.

Workarounds

Microsoft has not identified any workarounds for this vulnerability.

Security Update Deployment

For Security Update Deployment information, see the Microsoft Knowledge Base article referenced in the Executive Summary.

Acknowledgments

Microsoft recognizes the efforts of those in the security community who help us protect customers through coordinated vulnerability disclosure. See Acknowledgments for more information. 

Disclaimer

The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

Revisions

• V1.0 (October 11, 2016): Bulletin published.
• V1.1 (October 12, 2016): This bulletin has been revised to change the severity to Critical. This is an informational change only.

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