Microsoft has released Windows 10 KB5120249 as part of the August 2026 Patch Tuesday rollout. The cumulative update is available for eligible devices enrolled in the Extended Security Updates (ESU) program and supported Windows 10 Enterprise LTSC editions.
Installing KB5120249 upgrades Windows 10 version 22H2 to Build 19045.7663 and Enterprise LTSC 2021 to Build 19044.7663. In addition to August 2026 security patches, KB5120249 also fixes several compatibility issues, expands the rollout of updated Secure Boot certificates, and fixes a File History backup error affecting SMB network shares. Here’s everything you need to know about the Windows 10 KB5120249 update released on August 11, 2026.
What’s New in Windows 10 KB5120249?
Windows 10 KB5120249 is primarily a security and quality update rather than a feature release. It includes two notable Windows improvements along with the latest security fixes.
- Fixes File History backup problems: Microsoft resolved an issue where automatic File History backups to SMB network shares could fail with an “invalid credentials” error. Scheduled backups could therefore fail to copy files to the network location.
- Expands Secure Boot certificate coverage: KB5120249 adds high-confidence device-targeting data, allowing more eligible Windows 10 PCs to receive updated Secure Boot certificates through Windows Update.
Security Fixes in Windows 10 KB5120249
Security is the main reason to install this month’s update. Microsoft’s broader August 2026 Patch Tuesday release addresses 421 CVEs across its products, including three zero-day vulnerabilities. One was actively exploited, while the others had been publicly disclosed.
The most urgent is CVE-2026-68820, a Windows Ancillary Function Driver for WinSock elevation-of-privilege vulnerability that Microsoft says is being actively exploited.
For eligible Windows 10 users, KB5120249 provides the latest monthly security protections available for supported systems.
Known Issues
Microsoft is not currently aware of any known issues with KB5120249.
Because the update was released recently, Microsoft may update its release information if new problems are confirmed.
How to Install Windows 10 KB5120249
If your PC is eligible for the update, you can install KB5120249 through Windows Update.
- Windows Update – Go to Settings > Update & Security > Windows Update and check for updates.
- Microsoft Update Catalog – You can manually download the standalone package from the Microsoft Update Catalog. (64-bit systems, ARM64 systems)
- Windows Server Update Services (WSUS) – For enterprise environments, KB5120249 will sync automatically if configured.
Windows 10 KB5120249 Direct Download Links: 64-bit and 32-bit (x86).
Note: The link above to the Windows 10 offline installer opens Microsoft’s Update Catalog. You need to click the “Download” button next to the Windows 10 version compatible with your system, then click the .msu link in the pop-up to begin the download.
If you are looking for the Windows 10 version 22H2 ISO, you can get it from here.
Frequently Asked Questions (FAQ)
No — this update is part of the ESU program. If you see it but aren’t enrolled, the install may fail or you may not receive future updates.
You can install it via Windows Update, the Microsoft Update Catalog, or enterprise tools such as WSUS.
No. The update focuses on security, reliability, File History, and Secure Boot improvements rather than introducing major new Windows 10 features.
Ensure you have a stable internet connection, run the Windows Update troubleshooter, verify ESU enrolment, and consider a manual installation via the Update Catalog.
