December 3, 2018—KB4478877 (OS Build 14393.2641)

Applies to: Windows 10 Version 1607Windows Server 2016

Improvements and fixes


This update includes quality improvements. No new operating system features are being introduced in this update. Key changes include:

  • Addresses an issue that prevents the release of the on-demand Source Network Address Translation (SNAT) port allocated to a virtual machine (VM) after the SNAT port is no longer in use. As a result, the SNAT port becomes exhausted.

If you installed earlier updates, only the new fixes contained in this package will be downloaded and installed on your device.

Known issues in this update


Symptom Workaround

After you install the August Preview of Quality Rollup or September 11, 2018 .NET Framework update, instantiation of SqlConnection can throw an exception. For more information about this issue, see the following article in the Microsoft Knowledge Base:

4470809 SqlConnection instantiation exception on .NET 4.6 and later after August-September 2018 .NET Framework updates.

Microsoft is working on a resolution and will provide an update in an upcoming release.

After installing this update, users may not be able to use the Seek Bar in Windows Media Player when playing specific files. This issue does not affect normal playback.

This issue is resolved in KB4471321.
When features related to end-user-defined characters (EUDC) are used, the entire system may become unresponsive.

This issue is resolved in KB4471321.

After installing this update on Windows Server 2016, instant search in Microsoft Outlook clients fail with the error, "Outlook cannot perform the search".

To alleviate the symptoms, run sfc /scannow as described in step 3 of Use the System File Checker tool to repair missing or corrupted system files. Then restart Microsoft Outlook.

Microsoft is working on a resolution and will provide an update in an upcoming release.

How to get this update


Before installing this update

Microsoft strongly recommends you install the latest servicing stack update (SSU) for your operating system before installing the latest cumulative update (LCU). SSUs improve the reliability of the update process to mitigate potential issues while installing the LCU. For more information, see Servicing stack updates.

If you are using Windows Update, the latest SSU (KB4465659) will be offered to you automatically. To get the stand-alone package for the latest SSU, go to the Microsoft Update Catalog

Install this update

To download and install this update, go to Settings > Update & Security > Windows Update and select Check for updates.

To get the stand-alone package for this update, go to the Microsoft Update Catalog website.

File information

For a list of the files that are provided in this update, download the file information for cumulative update 4478877.