Description of the security update for Outlook 2016: October 13, 2020

Applies to: Outlook 2016


This security update resolves a remote code execution vulnerability that exists in Microsoft Outlook if the software does not correctly handle objects in memory. It also resolves a denial of service vulnerability that exists in Microsoft Exchange Server if the software does not correctly handle objects in memory. To learn more about these vulnerabilities, see Microsoft Common Vulnerabilities and Exposures CVE-2020-16947 and Microsoft Common Vulnerabilities and Exposures CVE-2020-16949.

Note To apply this security update, you must have the release version of Outlook 2016 installed on the computer.

Be aware that the update in the Microsoft Download Center applies to the Microsoft Installer (.msi)-based edition of Office 2016. It doesn't apply to the Office 2016 Click-to-Run editions, such as Microsoft Office 365 Home (see What version of Office am I using?).

Improvements and fixes

This security update contains fixes for the following nonsecurity issues:
  • Fixes an issue that causes Outlook to intermittently crash when users interact with calendar items.
  • Fixes an issue to correctly block users from being able to forward multiple selected messages that have the "Do Not Forward" policy applied.
  • Fixes an issue in which the LegacyExchangeDN value for an email sender is preserved and displayed in the From field after a draft of the email is moved from a mailbox that has assistant permissions to the manager's mailbox.
  • Fixes an issue that causes the computers of some users to fail when they connect through MAPI/HTTP.

How to get and install the update

Method 1: Microsoft Update

This update is available from Microsoft Update. When you turn on automatic updating, this update will be downloaded and installed automatically. For more information about how to get security updates automatically, see Windows Update: FAQ.

Method 2: Microsoft Update Catalog

To get the standalone package for this update, go to the Microsoft Update Catalog website.

Method 3: Microsoft Download Center

You can get the standalone update package through the Microsoft Download Center. Follow the installation instructions on the download page to install the update.

More information

Security update deployment information

For deployment information about this update, see security update deployment information: October 13, 2020.

Security update replacement information

This security update replaces previously released security update 4484475.

File hash information

File name SHA1 hash SHA256 hash
outlook2016-kb4486671-fullfile-x86-glb.exe 6FE22B3267D69F0C5167D5126790A9D8FB35780A DA5F46065AF2AEA6F03816EA2C6E3B10941161AB0B0305FC1251FC5DCC1E137F
outlook2016-kb4486671-fullfile-x64-glb.exe 6ECA2A118B23B4CA4414D1D19825DB577D29B592 D86671F596F08E9DF2A78DA35F4C39961D1DD244AC6C27DF852558A8ADCF6411

File information

The English (United States) version of this software update installs files that have the attributes that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). The dates and times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and times may change when you perform certain operations on the files.

Information about protection and security

Protect yourself online: Windows Security support

Learn how we guard against cyber threats: Microsoft Security