Table of contents
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Release Date:

2/24/2021

Version:

2004-OS Build 19041.844 and 20H2-OS Build 19042.844

NEW 2/24/21
IMPORTANT As part of the end of support for Adobe Flash, KB4577586 is now available as an optional update from Windows Update (WU) and Windows Server Update Services (WSUS). Installing KB4577586 will remove Adobe Flash Player permanently from your Windows device. Once installed, you cannot uninstall KB4577586. For more details about Microsoft’s plans, see Update on Adobe Flash Player End of Support.

11/17/20

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 2004  update history home page.


Note Follow @WindowsUpdate to find out when new content is published to the release information dashboard.

 Highlights

  •  Updates an issue that displays unexpected screens during the Windows Out of Box Experience (OOBE). 

  • Updates an issue in Advanced display settings that shows the incorrect refresh rates available for high dynamic range (HDR) displays. 

  • Updates an issue that might cause video playback to flicker when rendering on certain low-latency capable monitors. 

  • Updates an issue that sometimes prevents the input of strings into the Input Method Editor (IME). 

  • Updates an issue that might sometimes prevent some keyboard keys from working, such as the home, Ctrl, or left arrow keys. This issue occurs when you set the Japanese IME input mode to Kana. 

  • Updates an issue that displays the wrong language when you sign in to a console after you change the system locale. 

  • Updates an issue with screen rendering after opening games with certain hardware configurations. 

  • Displays the proper Envelope media type as a selectable output paper type for Universal Print queues. 

Improvements and fixes

Note: To view the list of addressed issues, click or tap the OS name to expand the collapsible section.

  • This update makes quality improvements to the servicing stack, which is the component that installs Windows updates. Servicing stack updates (SSU) ensure that you have a robust and reliable servicing stack so that your devices can receive and install Microsoft updates.

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

  • This build includes all the improvements from Windows 10, version 2004.

  • Improves the ability of the WinHTTP Web Proxy Auto-Discovery Service to ignore invalid Web Proxy Auto-Discovery Protocol (WPAD) URLs that the Dynamic Host Configuration Protocol (DHCP) server returns.

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

  • Addresses an issue with a memory leak in Internet Explorer 11 that occurs when you use the Chinese language pack.

  • Addresses an issue with certain COM+ callout policies that cause a deadlock in certain applications.

  • Addresses an issue that prevents certain Win32 apps from opening as a different user when you use the runas command.

  • Addresses an issue that displays unexpected screens during the Windows Out of Box Experience (OOBE).

  • Addresses an issue that might cause a deadlock when a COM server delivers an event to multiple subscribers in parallel.

  • Addresses an issue in Advanced display settings that shows the incorrect refresh rates available for high dynamic range (HDR) displays.

  • Addresses an issue that might prevent certain CAD applications from opening if those applications rely on OpenGL.

  • Addresses an issue that might cause video playback to flicker when rendering on certain low-latency capable monitors.

  • Addresses an issue that sometimes prevents the input of strings into the Input Method Editor (IME).

  • Addresses an issue that exhausts resources because Desktop Windows Manager (DWM) leaks handles and virtual memory in Remote Desktop sessions.

  • Addresses an issue with a stop error that occurs at startup.

  • Addresses an issue that might delay a Windows Hello for Business (WHfB) Certificate Trust deployment when you open the Settings-> Accounts-> Sign-in Options page.

  • Addresses an issue that might sometimes prevent some keyboard keys from working, such as the home, Ctrl, or left arrow keys. This issue occurs when you set the Japanese IME input mode to Kana.

  • Removes the history of previously used pictures from a user account profile.

  • Addresses an issue that displays the wrong language when you sign in to a console after you change the system locale.

  • Addresses an issue that causes the host process of Windows Remote Management (WinRM) to stop working when it formats messages from a PowerShell plugin.

  • Addresses an issue in the Windows Management Instrumentation (WMI) service that causes a heap leak each time security settings are applied to WMI namespace permissions.

  • Addresses an issue with screen rendering after opening games with certain hardware configurations.

  • Improves startup times for applications that have roaming settings when User Experience Virtualization (UE-V) is turned on.

  • Addresses an issue in which a principal in a trusted MIT realm fails to obtain a Kerberos service ticket from Active Directory domain controllers (DC). This occurs on devices that installed Windows Updates that contain CVE-2020-17049 protections and configured PerfromTicketSignature to 1 or higher. These updates were released between November 10, 2020 and December 8, 2020. Ticket acquisition also fails with the error, “KRB_GENERIC_ERROR”, if callers submit a PAC-less Ticket Granting Ticket (TGT) as an evidence ticket without providing the USER_NO_AUTH_DATA_REQUIRED flag.

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

  • Enhances data loss prevention and insider risk management solution functionalities in Microsoft 365 endpoints.

  • Addresses an issue that displays an error when you attempt to open an untrusted webpage using Microsoft Edge Legacy or open an untrusted Microsoft Office document. The error is, "WDAG Report - Container: Error: 0x80070003, Ext error: 0x00000001". This issue occurs after installing the .NET update KB4565627.

  • Addresses an issue that prevents wevtutil from parsing an XML file.

  • Addresses an issue that fails to report an error when the Elliptic Curve Digital Signature Algorithm (ECDSA) generates invalid keys of 163 bytes instead of 165 bytes.

  • Adds support for using the new Chromium-based Microsoft Edge as the assigned access single kiosk app. Now, you can also customize a breakout key sequence for single app kiosks. For more information, see Configure Microsoft Edge kiosk mode.

  • Addresses an issue with User Datagram Protocol (UDP) broadcast packets that are larger than the maximum transmission unit (MTU). Devices that receive these packets discard them because the checksum is not valid.

  • Addresses an issue in which the WinHTTP AutoProxy service does not comply with the value set for the maximum Time To Live (TTL) on the Proxy Auto-Configuration (PAC) file. This prevents the cached file from updating dynamically.

  • Displays the proper Envelope media type as a selectable output paper type for Universal Print queues.

  • Ends the display of a random paper size for a printer when it uses the Microsoft Internet Printing Protocol (IPP) Class Driver.

  • Addresses an issue that might cause the IKEEXT service to stop working intermittently.

  • Addresses an issue that might prevent a Non-Volatile Memory Express (NVMe) device from entering the proper power state.

  • Addresses an issue that might cause stop error 7E in nfssvr.sys on servers running the Network File System (NFS) service.

  • Addresses an issue that prevents the User Profile Service from detecting a slow or a fast link reliably.

  • Addresses an issue that causes contention for a metadata lock when using Work Folders.

  • Adds a new dfslogkey as described below:

    • Keypath: HKEY_LOCAL_MACHINE/SOFTWARE/MICROSOFT/dfslog.

    • The RootShareAcquireSuccessEvent field has the following possible values:

      • Default value = 1; enables the log.

      • Value other than 1; disables the log.

     If this key does not exist, it will be created automatically. To take effect, any change to
     dfslog/RootShareAcquireSuccessEvent in the registry requires that you restart the DFSN service. 

  • Updates the Open Mobile Alliance (OMA) Device Management (DM) sync protocol by adding a check-in reason for requests from the client to the server. The check-in reason will allow the mobile device management (MDM) service to make better decisions about sync sessions. With this change, the OMA-DM service must negotiate a protocol version of 4.0 with the Windows OMA-DM client.

  • Turns off token binding by default in Windows Internet (WinINet). 

  • Addresses an issue with failover in an environment that only has IPv6 clusters. If the failover cluster has been running for more than 24 days, attempts to do a failover might not succeed or might be delayed.

  • Addresses an issue that might cause an application to stop working when you open the application.

  • Addresses an issue that results in outdated group membership listings. This issue occurs because the Group Policy service (GPSVC) makes infrequent updates to the Windows Management Instrumentation (WMI) session. As a result, this slows the propagation of changes the Active Directory (AD) administrator makes to user or group membership.

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

Symptoms

Workaround

When using the Microsoft Japanese Input Method Editor (IME) to enter Kanji characters in an app that automatically allows the input of Furigana characters, you might not get the correct Furigana characters. You might need to enter the Furigana characters manually.

Note The affected apps are using the ImmGetCompositionString() function.

This issue is resolved in KB5005101.

When opening a document in Microsoft Word, Microsoft Excel, or any Microsoft Office applications, you might receive the error, "Microsoft Excel cannot open or save any more documents because there is not enough available memory or disk space". This issue only affects devices that have installed Microsoft Office apps from the Microsoft Store and are attempting to open a document that has triggered the use of the Protected View feature.

This issue is resolved using Known Issue Rollback (KIR). Please note that it might take up to 24 hours for the resolution to propagate automatically to non-managed devices. Restarting your device might help the resolution apply to your device faster. For enterprise-managed devices that have installed an affected update and encountered this issue, it can be resolved by installing and configuring a special Group Policy.

Note Devices need to be restarted after configuring the special Group Policy. To find out more about using Group Policies, see Group Policy Overview.

How to get this update

Before installing this update

Prerequisite:

Starting with this release, Microsoft will combine the latest servicing stack update (SSU) for your operating system with the latest cumulative update (LCU). To utilize this improvement, install the most recent standalone SSU (KB4598481) before installing this LCU. If you install this LCU before installing KB4598481, you might encounter error 0x800f0823 – CBS_E_NEW_SERVICING_STACK_REQUIRED. Close the error message and install the recommended SSU. 

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

Install this update

Release Channel

Available

Next Step

Windows Update or Microsoft Update

Yes

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

Yes

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

Windows Server Update Services (WSUS)

No

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

If you want to remove the LCU

To remove the LCU after installing the combined SSU and LCU package, use the DISM/Remove-Package command line option with the LCU package name as the argument. You can find the package name by using this command: DISM /online /get-packages.

Running Windows Update Standalone Installer (wusa.exe) with the /uninstall switch on the combined package will not work because the combined package contains the SSU. You cannot remove the SSU from the system after installation.

File information

For a list of the files that are provided in this update, download the file information for cumulative update 4601382

For a list of the files that are provided in the servicing stack update, download the file information for the SSU - version 19041.841 and 19042.841

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