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Release Date:

13/04/2021

Version:

OS Builds 19041.928 and 19042.928

NEW 4/13/21
REMINDER
Microsoft removed the Microsoft Edge Legacy desktop application that is out of support in March 2021. In this April 13, 2021 release, we will install the new Microsoft Edge. For more information, see New Microsoft Edge to replace Microsoft Edge Legacy with April’s Windows 10 Update Tuesday release.

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 to improve security when Windows performs basic operations.

  • Updates to improve security when using input devices such as a mouse, keyboard, or pen.

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 security update includes quality improvements. Key changes include:

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

  • No additional issues were documented for this release.

Note: This release also contains updates for Microsoft HoloLens (OS Build 19041.1144) released April 13, 2021. Microsoft will release an update directly to the Windows Update Client to improve Windows Update reliability on Microsoft HoloLens that have not updated to this most recent OS Build.

This security update includes quality improvements. Key changes include:

  • 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 an issue with security vulnerabilities identified by a security researcher. Because of these security vulnerabilities, this and all future Windows updates will no longer contain the RemoteFX vGPU feature. For more information about the vulnerability and its removal, see CVE-2020-1036 and KB4570006. Secure vGPU alternatives are available using Discrete Device Assignment (DDA) in Windows Server LTSC releases (Windows Server 2016 and Windows Server 2019) and Windows Server SAC releases (Windows Server, version 1803 and later versions).

  • Addresses a potential elevation of privilege vulnerability in the way Azure Active Directory web sign-in allows arbitrary browsing from the third-party endpoints used for federated authentication. For more information, see CVE-2021-27092 and Policy CSP - Authentication.

  • Addresses an issue that causes Windows Back up using File History to stop working for a few users. This issue occurs after installing the February 9, 2021 update. The error message is, “Failed to start the backup of user links (error 8007005)”.

  • Security updates to Windows App Platform and Frameworks, Windows Apps, Windows Input and Composition, Windows Office Media, Windows Fundamentals, Windows Cryptography, the Windows AI Platform, Windows Kernel, Windows Virtualization, and Windows Media.

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

For more information about the resolved security vulnerabilities, please refer to the new Security Update Guide website.

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

Symptom

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.

Devices with Windows installations created from custom offline media or custom ISO image might have Microsoft Edge Legacy removed by this update, but not automatically replaced by the new Microsoft Edge. This issue is only encountered when custom offline media or ISO images are created by slipstreaming this update into the image without having first installed the standalone servicing stack update (SSU) released March 29, 2021 or later.

Note Devices that connect directly to Windows Update to receive updates are not affected. This includes devices using Windows Update for Business. Any device connecting to Windows Update should always receive the latest versions of the SSU and latest cumulative update (LCU) without any extra steps.

To avoid this issue, be sure to first slipstream the SSU released March 29, 2021 or later into the custom offline media or ISO image before slipstreaming the LCU. To do this with the combined SSU and LCU packages now used for Windows 10, version 20H2 and Windows 10, version 2004, you will need to extract the SSU from the combined package. Use the following steps to extract the using SSU:

  1. Extract the cab from the msu via this command line (using the package for KB5000842 as an example): expand Windows10.0-KB5000842-x64.msu /f:Windows10.0-KB5000842-x64.cab <destination path>

  2. Extract the SSU from the previously extracted cab via this command line: expand Windows10.0-KB5000842-x64.cab /f:* <destination path>

  3. You will then have the SSU cab, in this example named SSU-19041.903-x64.cab. Slipstream this file into your offline image first, then the LCU.

If you have already encountered this issue by installing the OS using affected custom media, you can mitigate it by directly installing the new Microsoft Edge. If you need to broadly deploy the new Microsoft Edge for business, see Download and deploy Microsoft Edge for business

A small subset of users have reported lower than expected performance in games after installing this update. Most users affected by this issue are running games full screen or borderless windowed modes and using two or more monitors.

This issue is resolved in KB5003690.

After installing this update, 5.1 Dolby Digital audio may play containing a high-pitched noise or squeak in certain apps when using certain audio devices and Windows settings.

Note This issue does not occur when stereo is used.

This issue is resolved in KB5003690.

How to get this update

Before installing this update

Prerequisite:

Microsoft now combines the latest servicing stack update (SSU) for your operating system with the latest cumulative update (LCU). If you encounter the error, 0x800f0823 – CBS_E_NEW_SERVICING_STACK_REQUIRED, close the error message and install the last standalone SSU (KB4598481) before installing this LCU. You will not need to install this SSU (KB4598481) again for future updates. 

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 and Microsoft Update

Yes

None. This update will be downloaded and installed automatically from Windows 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)

Yes

This update will automatically sync with WSUS if you configure Products and Classifications as follows:

Product: Windows 10, version 1903 and later

Classification: Security Updates

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 5001330

For a list of the files that are provided in the servicing stack update, download the file information for the SSU - version 19041.925 and 19042.925

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