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Windows 10 21H2 / 22H2 Windows 10 21H2 / 22H2 Security update
Patch Tuesday

KB5035845

KB5035845: Cumulative update for Windows 10, versions 21H2 and 22H2, March 2024. Hyper-V remote-code flaw addressed; Copilot icon issues remain

In short

Addresses 35 vulnerabilities, including two critical Hyper-V flaws. Copilot can still disrupt desktop icon placement on multi-monitor devices, and the update is no longer available from Microsoft’s release channels.

Does it affect you? Applies to: This update applies to Windows 10 version 22H2 and supported editions of version 21H2: Enterprise, Education, IoT Enterprise, Enterprise multi-session, Enterprise LTSC 2021, and IoT Enterprise LTSC 2021.

Builds
19044.4170 · 19045.4170
Security
35 fixed · 2 critical

What changes

Improvements 4 changes

Windows 10, version 22H2

For: Windows 10 version 22H2 devices

  • Version 22H2 includes the improvements from supported Windows 10 version 21H2 editions.1

Windows 10, version 21H2

2 items

For: Supported Windows 10 version 21H2 editions

  • The update includes quality improvements that were part of KB5034843.2
  • Internal Windows functionality receives miscellaneous security improvements.3

Servicing stack

For: Windows 10 devices

  • The component that installs Windows updates receives quality improvements.4
    Servicing stack builds 19044.4163 and 19045.4163.

Known issues

  1. Resolved Affects: Organizations and IT administrators Resolved by KB5040525

    After you install KB5034203 (dated 01/23/2024) or later updates, some Windows devices that use the [DHCP Option 235](https://learn.microsoft.com/tr…

    After KB5034203 or later, some devices using DHCP Option 235 might be unable to use Microsoft Connected Cache nodes and instead download updates and apps from the public internet. Home users are unlikely to experience this issue. KB5040525 addresses it.5

    Resolution Fixed in KB5040525

    Install KB5040525 (or a later cumulative update) on affected devices. No manual workaround is required after updating.

  2. Open Affects: Everyone

    Windows devices using more than one (1) monitor might experience issues with desktop icons moving unexpectedly between monitors or other icon alignment issues when attempting to use Copilot in Window…

    On devices using more than one monitor, desktop icons might move between monitors or have other alignment problems when using Copilot in Windows (in preview).6

    How to apply the workaround Workaround

    A new Copilot experience is gradually rolling out to devices with KB5039299 or later; Microsoft says it will address the issue.6

  3. Open Affects: Everyone

    Copilot in Windows (in preview) is not currently supported when your taskbar is located vertically on the right or left of your screen.

    Copilot in Windows (in preview) is not supported when the taskbar is positioned vertically on the right or left side of the screen.7

    How to apply the workaround Workaround

    A new Copilot experience is gradually rolling out to devices with KB5039299 or later; Microsoft says it will address the issue.7

Technical details

Data sheet · Security · Downloads · Components Click to collapse or expand

Data sheet

Released
2024-03-12
Type
Cumulative update
VersionBuildChannel
21H2 19044.4170 General availability
22H2 19045.4170 General availability

Security

35 vulnerabilities fixed
2 critical 33 important
VulnerabilitySeverityCVSS
CVE-2024-21407
Windows Hyper-V Remote Code Execution Vulnerability
 Critical 8.1
CVE-2024-21408
Windows Hyper-V Denial of Service Vulnerability
 Critical 5.5

The table lists the 2 exploited, publicly disclosed or critical vulnerabilities. See all 35 vulnerabilities →

Sources

Updated
Cited passages from Microsoft's official notes (7)
  1. 1. This build includes all the improvements from the supported Windows 10, version 21H2 editions. support.microsoft.com
  2. 2. This security update includes quality improvements that were a part of update KB5034843 (released February 27, 2024). support.microsoft.com
  3. 3. This update makes miscellaneous security improvements to internal OS functionality. support.microsoft.com
  4. 4. This update makes quality improvements to the servicing stack, which is the component that installs Windows updates. support.microsoft.com
  5. 5. This issue is addressed in KB5040525. support.microsoft.com
  6. 6. We are gradually rolling out a new Copilot experience for devices with KB5039299 or later updates installed. This new experience will address this issue. support.microsoft.com
  7. 7. Copilot in Windows (in preview) is not currently supported when your taskbar is located vertically on the right or left of your screen. support.microsoft.com
Checked automatically: 7 of 8 checks passed, 7 quoted passages · compared with Microsoft's page on Nov 8, 2026
  • Quotes found in the official pages: passed
  • Numbers found in the sources: passed
  • Vulnerabilities from the dossier only: passed
  • Links to allowed domains only: passed
  • Every official change covered: passed
  • Readable plain text: passed
  • Changes confirmed by the file list: passed
  • Sources agree: not passed

A second AI read the text against the sources: correctness 5/5, clarity 4/5, completeness 4/5. How we work

Published by The Update Bureau. Written with AI from Microsoft's own documents, checked by rules and a second AI. How we work · Report a mistake