Businesses still running Windows 10 can close this month’s security gaps now: Microsoft released the Windows 10 KB5126657 extended security update on October 13, 2026, bundling the October 2026 Patch Tuesday fixes with several bug fixes and changes. The update applies to devices on Windows 10 Enterprise LTSC or enrolled in the Extended Security Updates (ESU) program, and it raises Windows 10 to build 19045.7807 and Windows 10 Enterprise LTSC 2021 to build 19044.7807. Microsoft rates the package Critical.
What happened
According to BleepingComputer, Microsoft released the cumulative security update KB5126657 for Windows 10, which carries this month’s Patch Tuesday fixes. Microsoft’s official advisory confirms the update covers Windows 10 ESU, Windows 10 Enterprise LTSC 2021 and Windows 10 IoT Enterprise LTSC 2021. BleepingComputer reports that the October 2026 Patch Tuesday fixed 1,411 vulnerabilities across Microsoft’s products, including one actively exploited zero-day flaw.
Are you affected?
This update is for Windows 10 devices that are still receiving security patches through a paid or licensed channel. Microsoft’s advisory lists it as applying to Windows 10 ESU, Windows 10 Enterprise LTSC 2021 and Windows 10 IoT Enterprise LTSC 2021. Mainstream Windows 10 Home and Pro installations that are not enrolled in ESU do not receive this package.
To check where your machines stand, confirm the Windows build number after installing. A patched device reports build 19045.7807 for Windows 10, version 22H2 and 21H2, or 19044.7807 for Windows 10 Enterprise LTSC 2021. Microsoft notes that reaching version 22H2 requires the enablement package EKB KB5015684.
One known issue carries over from earlier updates. Microsoft says some USB Audio Class 1.0 devices may fail after the September 8, 2026 security update, showing a “This device cannot start (Code 10)” error in Device Manager, producing no audio, or leaving volume controls and sound settings unresponsive. Some devices work in standard stereo but fail with 8-channel or 3D audio. Microsoft partially resolved this in an out-of-band update on September 14, 2026, which addressed the 8-channel and 3D audio symptoms, and says it is still working on the remaining problems. Microsoft notes that some customers restored audio by switching the device to 2-channel mode.
What to do now
- Confirm which Windows 10 machines are covered. Identify any devices on Enterprise LTSC 2021 or enrolled in ESU, since those are the systems this update targets.
- Install KB5126657 through Settings, then Windows Update, then Check for Updates. If earlier updates are already installed, only the new components download.
- Verify the build number after installing. Look for 19045.7807 or 19044.7807 to confirm the patch applied.
- Test audio on any device that uses a USB Audio Class 1.0 interface. If a device fails with a Code 10 error or loses sound, Microsoft’s listed step is to switch it to 2-channel mode while it works on further fixes.
- Review ReFS and Storage Spaces configurations if you use them, since this update changes behavior in both areas, described below.
What changed in KB5126657?
Microsoft no longer ships new features for Windows 10, so KB5126657 is mainly security updates and bug fixes. The advisory documents the following changes.
- Date and time: The update enables permanent Daylight Saving Time support for British Columbia and Alberta starting in November 2026, and introduces a new time zone, Manitoba Standard Time (UTC-05:00) Manitoba.
- ReFS security: The update adds auditing and optional policy controls for ReFS volumes on externally attached storage devices. Auditing is on by default, while enforcement controls stay off by default to give administrators time to evaluate future hardening changes. Microsoft documents this in KB5130741.
- Storage Spaces: The update fixes an issue that could leave some Storage Spaces Direct virtual disks offline after a Windows update, which happened when valid tiered storage metadata was wrongly flagged as invalid during recovery and kept affected disks and their workloads from coming online.
- File History: The update fixes a problem where File History could fail to back up or restore files to an external drive or network location, and could show a “Reconnect your drive” message even with a working backup drive connected.
- Secure Boot: The update continues rolling out updated Secure Boot certificates to eligible devices, with deployment through Windows Update ongoing across supported devices.
What this means for a small-business IT setup
For offices keeping Windows 10 alive on a licensed footing, KB5126657 is the vehicle for this month’s critical fixes, so applying it promptly closes the gaps patched on Patch Tuesday, including the zero-day Microsoft says is being actively exploited. The Storage Spaces and File History fixes matter for shops that rely on pooled storage or built-in backup, since both address failures that could leave disks offline or backups unavailable.
The timeline is worth marking on a calendar. Microsoft’s advisory states that free support for Windows 10 Enterprise LTSC 2021 ends on January 12, 2027, and points administrators to its Extended Security Updates licensing guidance for continuing coverage. Planning the move off Windows 10, or the ESU enrollment to keep patches flowing, is work an IT team can start now rather than at the deadline. The Microsoft Update Catalog lists the 22H2 x64 package at about 1,179 MB, which is useful for sizing deployment over metered or slower connections.
FAQ
Who can install Windows 10 KB5126657?
The update applies to Windows 10 ESU, Windows 10 Enterprise LTSC 2021 and Windows 10 IoT Enterprise LTSC 2021. If you run Windows 10 Enterprise LTSC or are enrolled in the ESU program, you can install it through Settings, Windows Update, then Check for Updates. After installing, Windows 10 updates to build 19045.7807 and Enterprise LTSC 2021 to build 19044.7807.
How many vulnerabilities does the October 2026 Patch Tuesday fix?
BleepingComputer reports that the October 2026 Patch Tuesday fixed 1,411 vulnerabilities across Microsoft’s products, including one actively exploited zero-day flaw. Those fixes are included in KB5126657.
Is there a known issue after installing this update?
Yes. Microsoft says some USB Audio Class 1.0 devices may fail with a Code 10 error, lose audio, or have unresponsive volume and sound controls after the September 8, 2026 security update. An out-of-band update on September 14, 2026 partially resolved it for 8-channel and 3D audio modes, and Microsoft is still working on the remaining symptoms. Some customers restored audio by switching to 2-channel mode.