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Release Date:



OS Build 17763.1613

Because of minimal operations during the holidays and the upcoming Western new year, there won’t be a preview release (known as a “C” release) for the month of December 2020. There will be a monthly security release (known as a “B” release) for December 2020. Normal monthly servicing for both B and C releases will resume in January 2021.

For information about Windows update terminology, see the article about the types of Windows updates and the monthly quality update types. To view other notes and messages, see the Windows 10, version 1809 update history home page.


  • Updates an issue that causes the Chromium-based Microsoft Edge browser to open in the background when a device is in tablet mode.

  • Updates an issue that causes the hard drive to fill up in certain error situations.

Improvements and fixes

This non-security update includes quality improvements. Key changes include:

  • Updates Internet Explorer’s About dialog to use the standard modern dialog.

  • Addresses an issue that causes the Chromium-based Microsoft Edge browser to open in the background when a device is in tablet mode.

  • Addresses an issue that causes the hard drive to fill up in certain error situations.

  • Addresses an issue that generates a 0x57 error when the wecutil ss /c: command is used to update an Event Forwarding subscription.

  • Addresses an issue that causes applications to fail when they call the LookupAccountSid() API. This occurs after migrating accounts to a new domain whose name is shorter than the name of the previous domain.

  • Addresses an issue that causes Windows Defender Application Control to generate too many events related to dynamic code generation.

  • Addresses an issue that causes the “I forgot my Pin" functionality on the lock screen to fail. This failure occurs if the user has signed in using a username and password and the DontDisplayLastUserName or HideFastUserSwitching policy settings are enabled.

  • Addresses an issue that causes a system to stop working during startup. This occurs when the CrashOnAuditFail policy is set to 1 and command-line argument auditing is turned on.

  • Addresses an issue that prevents access to Azure Active Directory (AD) using the Google Chrome browser because of a Conditional Access policy error.

  • Addresses an issue that causes the Microsoft Management Console (MMC) Group Policy application to stop working when you are editing the Group Policy Security settings. The error message is, “MMC cannot initialize the snap-in.”

  • Addresses an issue that fails to free a system’s non-paged pool and requires a restart of the system. This occurs when running 32-bit applications with the Federal Information Processing Standard (FIPS) mode enabled.

  • Extends Microsoft Defender for Endpoint support to new regions.

  • Addresses high memory and CPU utilization in Microsoft Defender for Endpoint.

  • Addresses an issue in the Microsoft Remote Procedure Call (RPC) runtime that causes the Distributed File System Replication (DFSR) service to stop responding. This issue generates log events for DFS Replication (5014), RPC (1726), and no reconnection (5004) for a default timeout of 24 hours with no replication.

  • Addresses an issue that might cause Dynamic Host Configuration Protocol (DHCP) servers to ignore Link Selection information (DHCP Option 82, sub-option 5) in DHCP Request packets from clients.

  • Addresses an issue that prevents the PDF24 app, version 9.1.1, from opening .txt files.

  • Addresses an issue that might cause a non-paged pool memory leak in a Remote Desktop Protocol (RDP) over virtual private network (VPN) scenario.

  • Addresses an issue that might cause a memory leak in bindflt.sys when copying files in a container scenario.

  • Addresses an issue with Active Directory Certificate Services (AD CS) that might prevent Certificate Transparency (CT) logs from being submitted, if enabled.

  • Addresses an issue that fails to implement the terminal services (termsrv.dll) idle timeout settings.

  • Addresses an issue with the User Datagram Protocol (UDP) rate controller feature that causes Remote Desktop Services (Terminal Services) to intermittently stop working. As a result, all RDP connections are lost.

  • Addresses an issue with incorrect Canonical Display Driver (CDD) buffer flushing, which degrades performance in Remote Desktop Protocol (RDP) Windows 2000 Display Driver Model (XDDM) scenarios. This issue affects applications that use graphics processing units (GPU) to operate, such as Microsoft Teams, Microsoft Office, and web browsers.

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

Windows Update Improvements

Microsoft has released an update directly to the Windows Update client to improve reliability. Any device running Windows 10 configured to receive updates automatically from Windows Update, including Enterprise and Pro editions, will be offered the latest Windows 10 feature update based on device compatibility and Windows Update for Business deferral policy. This doesn't apply to long-term servicing editions.

Known issues in this update



After installing KB4493509, devices with some Asian language packs installed may receive the error, "0x800f0982 - PSFX_E_MATCHING_COMPONENT_NOT_FOUND."

  1. Uninstall and reinstall any recently added language packs. For instructions, see Manage the input and display language settings in Windows 10.

  2. Select Check for Updates and install the April 2019 Cumulative Update. For instructions, see Update Windows 10.

Note If reinstalling the language pack does not mitigate the issue, reset your PC as follows:

  1. Go to the Settings app > Recovery.

  2. Select Get Started under the Reset this PC recovery option.

  3. Select Keep my Files.

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 general information about SSUs, see Servicing stack updates and Servicing Stack Updates (SSU): Frequently Asked Questions.

If you are using Windows Update, the latest SSU (KB4587735) will be offered to you automatically. To get the standalone package for the latest SSU, search for it in the Microsoft Update Catalog.

Install this update

Release Channel


Next Step

Windows Update or Microsoft Update


Go to Settings > Update & Security > Windows Update. In the Optional updates available area, you’ll find the link to download and install the update.

Microsoft Update Catalog


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

Windows Server Update Services (WSUS)


You can import this update into WSUS manually. See the Microsoft Update Catalog for instructions.

File information

For a list of the files that are provided in this update, download the file information for cumulative update 4586839.

Note Some files erroneously have “Not applicable” in the “File version” column of the CSV file. This might lead to false positives or false negatives when using some third-party scan detection tools to validate the build.

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