February 9, 2021—KB4601319 (OS Builds 19041.804 and 19042.804)

EXPIRATION NOTICE****IMPORTANT As of 9/12/2023, this KB is only available from Windows Update. It is no longer available from the Microsoft Update Catalog or other release channels. We recommend that you update your devices to the latest security quality update.

11/17/20For 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.NoteFollow @WindowsUpdate to find out when new content is published to the release information dashboard.

Highlights

• Updates to improve security when using input devices such as a mouse, keyboard, or pen.
• Updates for verifying usernames and passwords.

Improvements and fixes

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

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Windows 10, version 20H2

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.

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Windows 10, version 2004

**Note:**This release also contains updates for Microsoft HoloLens (OS Build 19041.1136) released February 9, 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 a possible elevation of privilege vulnerability in the win32k component.
• Addresses an issue that might damage the file system of some devices and prevent them from starting up after running chkdsk /f.
• Updates the Netlogon Elevation of Privilege Vulnerability (CVE-2020-1472) to enable Enforcement mode. For more details, see CVE-2020-1472 and How to manage the changes in Netlogon secure channel connections associated with CVE-2020-1472.
• Security updates to the Windows App Platform and Frameworks, Windows Apps, Windows Input and Composition, Windows Cloud Infrastructure, Windows Management, Windows Authentication, Windows Fundamentals, Windows Cryptography, Windows Virtualization, Windows Core Networking, and Windows Hybrid Cloud Networking.
  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 ImprovementsMicrosoft 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 theImmGetCompositionString() function.	This issue is resolved in KB5005101.
Microsoft and Discord have found incompatibility issues with some games using Direct3D 12 when the in-game overlay feature of Discord is enabled. When attempting to open affected games you might receive an error, or the game might close silently.	To mitigate this issue, you can turn off the in-game overlay in settings within the Discord app.This issue is now resolved in an update to the Discord app. To verify you’re on the latest version, right click on the Discord icon in the notification area and select “Check for updates…”. If there are updates to install, it should install automatically but you might need to select the arrow icon in the upper right corner of the app to install the updated version. There is no update for Windows needed to resolve this issue.

How to get this update

Before installing this updateMicrosoft 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 (KB4598481) 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	No	No longer available.
Windows Server Update Services (WSUS)	No	No longer available.
File informationFor a list of the files that are provided in this update, download the file information for cumulative update 4601319.**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.