Table of contents
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Release Date:

4/13/2021

Version:

OS Build 14393.4350

3/9/21
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.

11/19/20
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 1607 update history home page

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

This security update includes quality improvements. Key changes include:

  • Updates the default values for the following Internet Explorer registry keys:

    • svcKBFWLink = “  ” (string with one empty space)

    • svcKBNumber = “  ” (string with one empty space)

    • svcUpdateVersion = 11.0.1000.

    In addition, these values will no longer be updated automatically. 

  • Address an issue that causes a system to stop working occasionally when users sign out or disconnect from remote sessions.

  • Addresses an issue with a heap leak that might cause explorer.exe to consume high amounts of memory.

  • Updates the Volgograd, Russia time zone from UTC+4 to UTC+3.

  • Adds a new time zone, UTC+2:00 Juba, for the Republic of South Sudan.

  • Addresses a race condition that causes PowerShell to stop working periodically and generates an Access Violation error. This issue occurs when you enable transcription on the system and run multiple PowerShell scripts simultaneously.

  • Addresses an issue that causes the sleep time defined in HKLM\Software\Microsoft\AppV\MAV\Configuration\MaxAttachWaitTimeInMilliseconds to be shorter than intended.

  • 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 high memory usage when performing XSLT transforms using MSXLM6.

  • Addresses an issue in spaceport.sys that might cause stop error 0x7E.

  • Addresses an issue with evaluating the compatibility status of the Windows ecosystem to help ensure application and device compatibility for all updates to Windows.

  • 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 an issue that prevents you from specifying up to 255 columns when you use the Jet Text installable indexed sequential access method (IISAM) format.

  • 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 Apps, Windows Input and Composition, Windows Office Media, Windows Fundamentals, Windows AI Platform, Windows Hybrid Cloud Networking, the Windows Kernel, 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

Microsoft is not currently aware of any issues with this update.

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 and applying Microsoft security fixes. 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 (KB5001402) 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

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

Classification: Security Updates

File information

For a list of the files that are provided in this update, download the file information for cumulative update 5001347

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