Summary
This non-security out-of-band (OOB) update for Windows 10, version 1809 and Windows Server 2019 (KB5134124) is cumulative. It includes updates from previous releases, along with additional non-security improvements.
Who should install this update
This out-of-band (OOB) update is intended for devices that do not receive current certificate trust list (CTL) updates, including updates to the list of untrusted certificates. Examples include devices in disconnected environments, devices that cannot access Microsoft’s certificate-update service and devices where automatic CTL updates are disabled.
Applies to: Windows Server 2019
This update includes fixes and quality improvements that are part of the following update:
The following is a summary of the issues that this update addresses when you install this update. The bold text within the brackets indicates the item or area of the change we are documenting.
- [Certificates] This update includes an updated trusted root certificate payload in the Windows cumulative update for devices that cannot access Microsoft’s certificate-update service and devices where automatic certificate trust list (CTL) updates are disabled. To learn more, see Certificates and trust in Windows.
Note If you installed earlier updates, only the new updates contained in this package will be downloaded and installed on your device.
For information about security vulnerabilities, see the Security Update Guide and October 2026 Security Updates.
Known issues in this update
Users might be unable to sign in to OWA or send emails on Exchange Server
Symptoms:
After installing this update, some on-premises Exchange servers might experience issues accessing or sending email. Users might be unable to sign in to Outlook on the web (OWA), or email messages sent from Outlook might remain in the Outbox and not be delivered. Additionally, Exchange might experience issues accessing mailboxes during mailbox replication.
In some affected configurations, Exchange Server OWA might fail with an error MapiExceptionMdbOffline: Unable to make connection to the server. (hr=0x80004005, ec=1142) with Event ID 1006 logged in the application log. Another reported symptom is growing email queues. Installing the October 2026 Exchange server security updates isn’t required for these issues to occur.
Workaround
This issue can be temporarily mitigated by modifying the registry key as described in Exchange servers may become unstable after installation of October 2026 Windows updates.
The October 2026 update introduced a default limit on the amount of memory used by Endpoint Mapper when handling Endpoint Lookup calls.
For workloads such as Exchange Server, the default limit of 512 simultaneous Endpoint Lookup calls might not be sufficient under heavy load. Administrators can use this registry setting to increase the maximum number of simultaneous Endpoint Lookup calls, which increases the amount of memory that Endpoint Mapper can use.
Microsoft Support: An additional mitigation is available for affected devices through Microsoft Support. To apply this mitigation in your organization, please contact Microsoft Support for business.
Next steps: Microsoft investigating this issue and will provide more information when it is available.
USB Audio Class 1.0 devices with error Code 10 or no output
Symptoms
After installing the September 8, 2026, Windows security update, some USB Audio Class 1.0 devices might fail to start or produce audio. Affected devices might experience one or more of the following symptoms:
- The device displays an error in Device Manager: "This device cannot start (Code 10).”
- No audio output.
- Volume controls are unresponsive or remain at zero.
- Sound settings are unresponsive or unavailable.
- Some devices might function in standard stereo configurations but fail when using multichannel audio features, including 8-channel or 3D audio modes. Some customers have reported that they're able to restore audio in these cases by switching to 2-channel mode.
This issue is limited to USB Audio Class 1.0 devices.
Resolution
This issue is partially resolved in the out-of-band (OOB) update released on September 14, 2026. This OOB update resolves the symptoms experienced on devices using 8-channel or 3D audio modes. Microsoft is working to address the other symptoms and will provide more information when it is available.
IT administrators who need an immediate workaround for the symptoms not addressed yet by the OOB update should contact Microsoft Support for Business for assistance.
Servicing stack update (KB5126650) - 17763.9354
Microsoft now combines the latest servicing stack update (SSU) for your operating system with the latest cumulative update (LCU). SSUs improves the reliability of the update process and includes fixes to the servicing stack, the component that installs Windows updates.
This servicing stack update (SSU) includes enhanced logic to verify whether a device is hosted on Azure, leveraging an updated certificate chain for validation. To ensure that the device can access the required certificate update domains to successfully download and install certificate updates, see Certificate downloads and revocation lists and Azure Certificate Authority details. To learn more about SSUs, see Servicing stack updates.
How to get this update
Before you install this update
For Windows Update: You must have the Windows update released on or after July 8, 2025 (such as KB5062557) installed before installing this update.
For Windows Server Update Services (WSUS) deployment or when installing the standalone package from Microsoft Update Catalog: You must have the Windows update released on or after July 8, 2025 (such as KB5062557) installed before installing this update.
Servicing Stack Update (SSU): You must have the latest SSU installed before installing this update.
Deployment
If you deploy dynamic updates such as this update to an existing Windows image, ensure the boot.stl file is included as part of the installation media. Failure to include the file might prevent devices from successfully starting from the installation media and can result in error code 0xc0430001.
Note
The boot.stl file is used during Secure Boot validation and must match the Windows version and architecture of the image you are updating.
To ensure the boot.stl file is included as part of the installation media, do one of the following:
- Use the Update WinPE script to update an existing Windows image. (Recommended)
- Manually copy the boot.stl file from the device Windows\Boot\EFI folder to the corresponding folder on your installation media before deploying the update.
For information about how to apply Dynamic Update packages to existing Windows images, see Update Windows installation media with Dynamic Update.
Get and install this update
To get and install this update, use one of the following Windows or Microsoft release channels.
| Available | Next Step |
|---|---|
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This update is available from the Microsoft Update Catalog. |
File information
A list of the files that are included in this update are provided in a CSV (Comma delimited) (*.csv) file. The file can be opened in a text editor such as Notepad or in Microsoft Excel.
Note The English (United States) version of this software update might contain files for additional languages.
Download the file information for out-of-band update KB5134124.
Download the file information for SSU (KB5126650) - version 17763.9354.
References
For information about Windows update terminology, see types of Windows updates and monthly quality update types.
For an overview of Windows 10, version 1809 or Windows Server 2019, see its update history page.
Related topics
Microsoft Store application updates
Windows updates do not install Microsoft Store application updates. If you are an enterprise user, see Microsoft Store apps - Configuration Manager. If you are a consumer user, see Get updates for apps and games in Microsoft Store.Secure Boot certificate updates remain in progress as Microsoft transitions devices from certificates that began expiring in 2026 to newer certificates. Devices that have not yet received the newer certificates can continue to start and receive standard Windows updates. Microsoft will continue delivering the newer Secure Boot certificates to eligible devices through Windows Update.
End of support
Microsoft will no longer provide free software updates from Windows Update, technical assistance, or security fixes on the following end dates. We recommend that you upgrade to a later version of Windows Server.
- Windows 10 Enterprise LTSC 2019: January 9, 2029
- Windows Server 2019: January 9, 2029