October 14, 2025—KB5066586 (OS Build 17763.7919)
Applies To
Release Date:
14/10/2025
Version:
OS Build 17763.7919
Windows Secure Boot certificate expirationÂ
Important: Secure Boot certificates used by most Windows devices are set to expire starting in June 2026. This might affect the ability of certain personal and business devices to boot securely if not updated in time. To avoid disruption, we recommend reviewing the guidance and taking action to update certificates in advance. For details and preparation steps, see Windows Secure Boot certificate expiration and CA 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.
Support for Windows 10 has ended on October 14, 2025
After October 14, 2025, Microsoft will no longer provide free software updates from Windows Update, technical assistance, or security fixes for Windows 10. Your PC will still work, but we recommend moving to Windows 11.​​​​​​​​​​​​​​​​​​​​​
Support for Windows Server 2019 will end in January 2029
After January 9, 2029, Microsoft will no longer provide free software updates from Windows Update, technical assistance, or security fixes for Windows Server 2019. We recommend that you upgrade to a later version of Windows Server.
Summary
This article lists the security issues and quality improvements included in this security update.
Applies to: Win 10 Ent LTSC 2019, Win 10 IoT Ent LTSC 2019, and Windows 10 IoT Core LTSC
This security 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.
​​​[Input and Composition]
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Fixed: An issue with the Chinese Input Method Editor (IME). Private Unicode characters were shown incorrectly and did not meet GB18030 standard.
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Fixed: An issue that affects USER32 Edit controls. Surrogate pairs appear as empty boxes when text fields reach their length limit.
[Windows Remote Management (WinRM)]
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Fixed: An issue that affects PowerShell Remoting and WinRM in which commands time out after 600 seconds.
[Fax modem driver]
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This update removes the ltmdm64.sys driver. Fax modem hardware dependent on this specific driver will no longer work in Windows.
If you installed earlier updates, only the new updates contained in this package will be downloaded and installed on your device.
For more information about security vulnerabilities, please refer to the new Security Update Guide website and the October 2025 Security Updates.
For information about Windows update terminology, see the article about the types of Windows updates and the monthly quality update types. For an overview of Windows 10, version 1809, see its update history page.
Known issues in this update
We are currently not aware of any issues with this update.
Applies to: Windows Server 2019 (All editions)
This security 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.
​​​[Input and Composition]
-
Fixed: An issue with the Chinese Input Method Editor (IME). Private Unicode characters were shown incorrectly and did not meet GB18030 standard.
-
Fixed: An issue that affects USER32 Edit controls. Surrogate pairs appear as empty boxes when text fields reach their length limit.
[Windows Remote Management (WinRM)]
-
Fixed: An issue that affects PowerShell Remoting and WinRM in which commands time out after 600 seconds.
[Stability issue]
-
Fixed: This update addresses an issue observed in rare cases after installing the May 2025 security update and subsequent updates causing devices to experience stability issues. Some devices became unresponsive and stopped responding in specific scenarios.
[Fax modem driver]
-
This update removes the ltmdm64.sys driver. Fax modem hardware dependent on this specific driver will no longer work in Windows.
If you installed earlier updates, only the new updates contained in this package will be downloaded and installed on your device.
For more information about security vulnerabilities, please refer to the new Security Update Guide website and the October 2025 Security Updates.
For information about Windows update terminology, see the article about the types of Windows updates and the monthly quality update types. For an overview of Windows 10, version 1809, see its update history page.
Known issues in this update
We are currently not aware of any issues with this update.
Windows 10 servicing stack update (KB5066585) - version 17763.7912
Microsoft now combines the latest servicing stack update (SSU) for your operating system with the latest cumulative update (LCU). SSUs improve the reliability of the update process to mitigate potential issues while installing updates.
This update makes quality improvements to the servicing stack, which is the component that installs Windows updates. To learn more about SSUs, see Servicing stack updates and Servicing Stack Updates (SSU): Frequently Asked Questions.
How to get this update
Before you install this update
You must have installed the August 10, 2021 SSU (KB5005112) before installing this cumulative update.
Install this update
To install this update, use one of the following Microsoft release channels.
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This update will be downloaded and installed automatically from Windows Update and Microsoft Update. |
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This update will be downloaded and installed automatically from Windows Update for Business in accordance with configured policies. |
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To get the standalone package for this update, go to the Microsoft Update Catalog website. For information about how to download and install updates from the Update Catalog, see How to download updates that include drivers and hotfixes from the Windows Update Catalog. |
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This update will automatically sync with Windows Server Update Services (WSUS) if you configure Products and Classifications as follows: Product: Windows 10 Classification: Security Updates |
If you want to remove the LCU
To remove the LCU after installing the combined SSU and LCU package, use the DISM/Remove-Package command line option with the LCU package name as the argument. You can find the package name by using this command: DISM /online /get-packages.
Running Windows Update Standalone Installer (wusa.exe) with the /uninstall switch on the combined package will not work because the combined package contains the SSU. You cannot remove the SSU from the system after installation.
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.
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