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Windows 10 21H2 / 22H2 Windows 10 21H2 / 22H2 Out-of-band update
Out-of-band

KB5129236

KB5129236: Cumulative update for Windows 10, versions 21H2 and 22H2, September 2026. Remote Desktop instability and USB multichannel audio fixed

In short

Fixes Remote Desktop failures, Linux VM shared-folder access, and 8-channel or 3D USB audio problems. Other USB Audio Class 1.0 symptoms remain unresolved.

Does it affect you? Applies to: Windows 10, version 22H2 devices covered by the ESU program, and Windows 10 Enterprise LTSC 2021 and Windows 10 IoT Enterprise LTSC 2021 devices on version 21H2.

Builds
19044.7727 · 19045.7727
Restart
Required
Review notes Additional details from the official release notes (1) Read note
  • In detail The fix addresses Plan9 folder-sharing problems in applications using HCS-managed virtual machines; it is not stated as a fix for all Linux virtual machines.

The official sources are linked at the end of the page.

What changes

Fixes 5 changes

Remote Desktop Services (known issue)

Verified in package 2 items

For: Remote Desktop environments

  • Remote Desktop connections and sign-ins, along with related tools, are less likely to fail or stop responding in affected environments.1
    Addresses instability after the September 2026 security update, including RDP connection and sign-in failures and servers becoming unresponsive during Remote Desktop configuration.
  • Remote Desktop connections and sign-ins, along with related tools, are less likely to fail or stop responding in affected environments.1
    Addresses instability after the September 2026 security update, including RDP connection and sign-in failures and servers becoming unresponsive during Remote Desktop configuration.

Hyper-V (known issue)

For: Applications using HCS-managed virtual machines

  • Linux virtual machines can see and access folders shared from the Windows host again.2
    Addresses folder-sharing issues with Plan9 in applications using HCS-managed virtual machines.

8-channel or 3D audio modes

Verified in package 2 items

For: Devices using USB Audio Class 1.0 audio

  • Some USB Audio Class 1.0 devices work with 8-channel or 3D audio modes again.3
    Resolves the multichannel audio symptoms for affected USB Audio Class 1.0 devices; other audio symptoms are not resolved by this update.
  • Some USB Audio Class 1.0 devices work with 8-channel or 3D audio modes again.3
    Resolves the multichannel audio symptoms for affected USB Audio Class 1.0 devices; other audio symptoms are not resolved by this update.

Improvement 1 change

Servicing stack

For: Devices undergoing Azure-hosting verification

  • The update improves how Windows checks whether a device is hosted on Azure.4
    The servicing stack update uses an updated certificate chain for Azure-hosting verification.

Known issues

  1. Resolved Affects: Everyone Resolved by KB5129236

    USB Audio Class 1.0 devices with error Code 10 or no output

    Some USB Audio Class 1.0 devices might still fail to start or produce audio, show Code 10, or have unresponsive volume controls or sound settings. The September 14 update resolves the 8-channel and 3D audio symptoms, but not the other symptoms.5

    Resolution Fixed in KB5129236

    Install KB5129236 (or a later cumulative update) on affected devices. No manual workaround is required after updating.

  2. Resolved Affects: Everyone Resolved by KB5126657

    File History might stop working after installing September 2026 Windows update

    Some File History users might be unable to create or update backups, see a false “Reconnect your drive” message, or find that previous versions are unavailable. This issue is resolved by later updates such as KB5126657.6

    Resolution Fixed in KB5126657

    Install KB5126657 (or a later cumulative update) on affected devices. No manual workaround is required after updating.

Technical details

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

Data sheet

Released
2026-09-14
Classification
Updates
Type
Cumulative update
Restart
Required
Replaces
KB5122878, KB5120249, KB5099539, KB5094127
+39 earlier KB5087544, KB5082200, KB5078885, KB5075912, KB5078129, KB5077796, KB5073724, KB5074976, KB5071546, KB5068781, KB5066791, KB5066198, KB5065429, KB5063842, KB5066188, KB5063709, KB5062649, KB5062554, KB5061087, KB5063159, KB5060533, KB5058481, KB5061979, KB5061768, KB5055612, KB5053643, KB5052077, KB5050081, KB5046714, KB5045594, KB5043131, KB5041582, KB5040525, KB5039299, KB5037849, KB5036979, KB5035941, KB5034843, KB5034203
Replaced by
KB5126657
VersionBuildChannel
21H2 19044.7727 General availability
22H2 19045.7727 General availability

Security

No vulnerabilities are listed for this update.

Updated components

38 files changed since the previous update for the same versions.

Top changed componentsFiles
Audio3
Remote Desktop3
Hyper-V and virtualization2

Verified in package: changed files confirm Remote Desktop Services (known issue), 8-channel or 3D audio modes.

Page history

  1. Known issue resolved: USB Audio Class 1.0 devices with error Code 10 or no output (KB5129236)

Sources

Updated
Cited passages from Microsoft's official notes (6)
  1. 1. In affected environments, RDS might become unstable, causing RDP connection and sign-in failures or servers to become unresponsive during Remote Desktop configuration. support.microsoft.com
  2. 2. Folders shared from the Windows host using Plan9 did not appear or could not be accessed in the guest environment. support.microsoft.com
  3. 3. This OOB update resolves the symptoms experienced on devices using 8-channel or 3D audio modes. support.microsoft.com
  4. 4. This servicing stack update (SSU) includes enhanced logic to verify whether a device is hosted on Azure, leveraging an updated certificate chain for validation. support.microsoft.com
  5. 5. This issue is partially resolved in the out-of-band (OOB) update released on September 14, 2026, (KB5129236), and updates released after this date. learn.microsoft.com
  6. 6. This issue is resolved in Windows updates released on and after October 13, 2026 such as KB5126657. support.microsoft.com
Checked automatically: 8 of 8 checks passed, 6 quoted passages · compared with Microsoft's page on Nov 13, 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: passed

A second AI read the text against the sources: correctness 3/5, 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