Today, October 14, 2025, marks a significant milestone in computing history: the official End of Support (EoS) for Microsoft Windows 10, version 22H2 (and earlier editions). As part of the October 2025 Patch Tuesday cycle, Microsoft has released the KB5066791 cumulative update, which is the final batch of free security and quality updates for the decade-old operating system. The KB5066791 update advances to Windows 10 build 19045.6456 and addresses numerous flaws, including several zero-day vulnerabilities.
Additionally, KB5066586 (OS Build 17763.7919) has been released for Windows 10 version 1809. Both updates contain multiple security fixes and general improvements to enhance overall system reliability and user experience.
This will be the last update for devices not enrolled in the WINDOWS 10 ESU PROGRAM.
Windows 10 KB5066791 Update
Installing KB5066791 cumulative update for Windows 10 versions 22H2 and 21H2 advances the respective OS builds to 19045.6456 and 19044.6456. The update focuses on security and addresses several lingering bugs:
- Critical Security Fixes: The update is part of the October 2025 Patch Tuesday, resolve a large number of security vulnerabilities across the Windows operating system.
- SMBv1 Connectivity Fix: It resolves an issue preventing connections to shared files or folders when using the Server Message Block (SMB) v1 protocol over NetBIOS (NetBT).
- PowerShell Remoting Timeout: A fix is included for an issue where PowerShell Remoting and Windows Remote Management (WinRM) commands would time out after 600 seconds.
- Autopilot Enrollment: It addresses a known issue where the Enrollment Status Page (ESP) might not complete successfully during the Out-of-Box Experience (OOBE) for devices using Windows Autopilot.
- Driver Removal: The update removes the ltmdm64.sys driver, which means fax modems dependent on this specific component will no longer function.
This update also introduces a servicing stack update (SSU) which incorporates an updated certificate chain to improve Azure environment validation. Fix Text display issues in Chinese IME and USER32 Edit controls, causing incorrect Unicode rendering and empty boxes for surrogate pairs.
Windows 10 Reaches End of Life
With the release of KB5066791, Microsoft has officially ended mainstream support for Windows 10. It means,
- No More Free Security Updates: Your PC will not automatically receive patches for future security flaws discovered in Windows 10.
- No More Free Quality/Bug Fixes: General improvements and non-security bug fixes will also stop.
- Vulnerability Risk: Continued use without security updates will expose your device to significant risks over time.
However, if your PC isn’t compatible with the newer OS (Windows 11), you can enroll in the Windows 10 Extended Security Updates (ESU) program, which continues to provide critical patches for one more year for free (until October 2026).
How to Download and Install Windows 10 KB5066791 Update
Since its mandatory updates bring critical fixes, Windows 10 KB5066791 downloads and installs automatically via Windows Update. To check for and install the update manually.
- Open Settings using Windows key + I.
- Click Update & Security, then Windows Update.
- In the right-hand pane, click on the Check for updates button.
- You will see the following patch, which automatically downloads and installs on your device.
2025-10 Cumulative Update for Windows 10 Version 22H2 for x86-based Systems (KB5066791)
Ensure your device is connected to a stable internet connection to download update files from the Microsoft server. Once done, you need to reboot your computer to apply the changes.
Alternatively, you can download the standalone installer directly from the Microsoft Update Catalog by searching for “KB5066791.”
Windows 10 KB5066791 Direct download links 64-bit and 32-bit (x86).
- locate the patch next to the correct edition and version of the operating system.
- To install the update, simply run the downloaded MSU file and Windows will automatically install the cumulative update.
- If you are looking for the latest Windows 10 version 22H2 ISO, click here.
- In addition, you can download the latest Windows 11 ISO images here.
Uninstall Windows 10 KB5066791
If installing KB5066791 causes issues on your device, you can uninstall the update to revert the changes.
Uninstall KB5066791 using the Windows Update History tool
- Go to Windows Settings (Windows key + I) > Update & Security > Windows Update.
- From the right-hand pane, click on View Update History.
- Now, click on Uninstall updates.
- Select Update for Microsoft Windows (KB5066791) and press the Uninstall button.
Uninstall KB5066791 using the command line
Another quick way to uninstall this update is by using the command prompt. Here are the commands:
- Open the Command Prompt (Run > cmd)
- Run the following command:
wmic qfe list brief /format:table - This will show all the updates installed on the computer. Make sure KB5066791 is on the list.
- To uninstall the update, run the following command
wusa /uninstall /kb:5066791
The system needs to be restarted after uninstalling the update.
In addition, Microsoft has noted that Windows 10 version 21H2 reached end of service, which means devices no longer receive monthly security and quality updates that contain protection from the latest security threats. Microsoft recommends installing the latest version 22H2 or Upgrade to Windows 11
How to Fix Common Issues with Windows 10 KB5066791
While the Windows 10 KB5066791 update brings important improvements and fixes, some users may experience problems during or after installation. Here are proven solutions to resolve the most common issues.
Run the Windows Update Troubleshooter
The built-in troubleshooter can automatically detect and fix update-related issues.
- Press Windows + I to open Settings.
- Go to Update & Security > Troubleshoot.
- Click Additional troubleshooters.
- Select Windows Update and click Run the troubleshooter.
- Follow the on-screen instructions and apply any recommended fixes.
Check Your Internet Connection
A weak or unstable internet connection can cause the update to fail or get stuck.
- Use a wired Ethernet connection instead of Wi-Fi for better stability.
- Restart your router or modem.
- Temporarily disable VPNs or proxy servers.
- Test your connection speed using a service like Speedtest
Clear the Windows Update Cache
Corrupted update files in the cache can cause installation failures.
- Press Windows + R, type services.msc, and press Enter.
- Right-click the Windows Update service and select Stop.
- Navigate to C:\Windows\SoftwareDistribution\Download and delete all files inside the folder.
- Go back to Services, right-click Windows Update, and choose Start.
- Try installing the update again from Settings > Update & Security > Windows Update.
Repair Corrupt System Files
Damaged or missing system files can lead to update errors. Running SFC and DISM can help.
Open Command Prompt as administrator and run the following commands:
- sfc /scannow
- DISM /Online /Cleanup-Image /RestoreHealth
This will scan for corrupt system files and the Windows image for corruption and try to repair them. Let the scanning complete 100%, once done, restart your PC and try installing the update again.
Check for Driver and Software Conflicts
Outdated or incompatible drivers can cause post-update issues like crashes or slow performance.
- Open Device Manager (Windows + X > Device Manager).
- Look for devices with a yellow warning icon and update their drivers.
- Update critical drivers (graphics, network, chipset) from the manufacturer’s website.
Windows 10 KB5066791– Frequently Asked Questions
What is Windows 10 KB5066791?
It’s the October 2025 cumulative update for Windows 10 version 22H2, OS Build 19045.6456, with security patches and bug fixes.
How do I get KB5066791?
Go to Settings > Update & Security > Windows Update and check for updates, or download it from the Microsoft Update Catalog.
Why is KB5066791 failing to install?
Common causes are corrupted update files, poor internet connection, or low disk space.
Can I uninstall KB5066791 if it causes issues?
Yes, from Settings > Update & Security > Update history > Uninstall updates, or by using System Restore.
Does KB5066791 include security fixes?
Yes, it addresses multiple security vulnerabilities and improves system stability.
Also read:
- Difference Between Windows 10 Feature Update and Cumulative Updates
- Windows Update won’t download or failed to install on Windows 10 (Solved)
- How to Share Files and Printers Between Two Windows 10 Computers
- Windows 10 keeps shutting down and restarting automatically. Try these solutions
- Complete Review of Microsoft Windows 10 Operating System
