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Windows Server 2025 Windows Server 2025 Out-of-band update
Out-of-band

KB5129235

KB5129235: Cumulative update for Windows Server, version 2025, September 2026. Remote Desktop failures fixed; USB audio partly restored

In short

Remote Desktop connections and sign-ins work again in affected environments. USB audio in 8-channel or 3D modes is also fixed, but other USB audio problems remain.

Does it affect you? Applies to: Devices running Windows Server 2025. The documented Remote Desktop issue affected some environments after the September 2026 security update.

Build
26100.33451
Restart
Required
Review notes Additional details from the official release notes (3) Read notes
  • What changes KB5129235 includes servicing stack update KB5122870 (build 26100.33434), which improves the component that installs Windows updates.
  • What to do For remaining USB audio symptoms, IT administrators who need an immediate workaround should contact Microsoft Support for Business.
  • Known issues For remaining USB audio symptoms, IT administrators who need an immediate workaround should contact Microsoft Support for Business.

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

What changes

Fixes 2 changes

Remote Desktop Services (known issue)

Verified in package
  • Remote Desktop connections and sign-ins work again in affected environments. Servers and related tools no longer stop responding during Remote Desktop setup.1
    Addresses the issue after KB5122871 that could make RDS unstable, causing RDP connection and sign-in failures or unresponsiveness during Remote Desktop configuration. MMC, RDS Licensing Diagnoser, File Explorer, and the Windows Update page could also stop responding.

8-channel or 3D audio modes

Verified in package

For: Devices using USB Audio Class 1.0

  • Some USB audio devices work again with 8-channel or 3D audio. Other reported USB audio problems are not fixed by this update.2
    Resolves the multichannel audio symptoms for USB Audio Class 1.0 devices. Other symptoms, such as Code 10 or no audio output, are not resolved.

Known issues

  1. Open Affects: Organizations and IT administrators

    Windows Server Update Services (WSUS) does not display error details

    WSUS does not show synchronization error details. This function was temporarily removed to address a remote code execution vulnerability.3

    Workaround status No workaround yet

    Microsoft has not published a manual workaround for this issue yet. Monitor release health until a resolving update is available.

  2. Resolved Affects: Everyone Resolved by KB5129235

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

    Some USB Audio Class 1.0 devices may still fail to start or produce sound after the September 8, 2026 security update. KB5129235 fixes the symptoms with 8-channel or 3D audio modes, but other symptoms remain.4

    How to apply the workaround Workaround

    For symptoms not fixed by this update, contact Microsoft Support for Business for assistance.4

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
KB5122871, KB5120233, KB5099536, KB5094125
+29 earlier KB5087539, KB5091157, KB5082063, KB5078740, KB5075899, KB5078135, KB5077793, KB5073379, KB5072033, KB5072359, KB5068861, KB5070881, KB5070773, KB5066835, KB5068221, KB5065426, KB5063878, KB5064489, KB5062553, KB5060842, KB5058411, KB5055523, KB5053598, KB5051987, KB5050009, KB5048667, KB5046617, KB5044284, KB5043080
Replaced by
KB5126646
VersionBuildChannel
2025 26100.33451 General availability

Security

No vulnerabilities are listed for this update.

Updated components

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

Top changed componentsFiles
Hyper-V and virtualization10
Graphics and display6
Networking4
Secure Boot4
Kernel3
Printing3
Audio2
File Explorer and shell2
Remote Desktop2
Settings2
Search1
Windows Update1

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 (KB5129235)

Sources

Updated
Cited passages from Microsoft's official notes (4)
  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. This OOB update resolves the symptoms experienced on devices using 8-channel or 3D audio modes. support.microsoft.com
  3. 3. This functionality is temporarily removed to address the Remote Code Execution Vulnerability, CVE-2025-59287. support.microsoft.com
  4. 4. This OOB update resolves the symptoms experienced on devices using 8-channel or 3D audio modes (last bullet point in the list of symptoms documented in this entry). learn.microsoft.com
Checked automatically: 8 of 8 checks passed, 4 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 3/5. 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