Microsoft Releases Critical Windows 10 Security Update KB5120249

Microsoft has released KB5120249, a critical security update for Windows 10 versions 22H2 and 21H2, along with Windows 10 Enterprise LTSC 2021 and Windows 10 IoT Enterprise LTSC 2021. The update is part of Microsoft’s Extended Security Updates (ESU) program and focuses on security fixes rather than new features.

File History Backup Issue Fixed

One of the notable fixes addresses a problem affecting File History automatic backups to network shares using SMB. In some cases, scheduled backups could fail with an “invalid credentials” error and fail to copy any files.

KB5120249 resolves this issue, allowing affected scheduled network backups to work correctly again.

Secure Boot Certificate Updates Continue

The update also includes additional device-targeting data designed to improve coverage for PCs eligible to automatically receive new Secure Boot certificates.

Microsoft says certificate deployment through Windows Update will continue across supported PCs and unmanaged business devices over the coming months. The change is part of Microsoft’s ongoing effort to replace outdated Secure Boot certificates on both Windows 10 and Windows 11 systems.

The update also includes changes to Microsoft Defender, the .NET Framework and the Windows Malicious Software Removal Tool, alongside the security vulnerabilities addressed by the patch.

How to Install KB5120249

KB5120249 will be installed automatically through Windows Update when it becomes available. Installation should take only a few minutes.

Users can also download the update manually through the Microsoft Update Catalog. The download is just under 1GB.

However, there is an important requirement: KB5120249 is only available to Windows 10 PCs enrolled in the ESU program.

ESU Keeps Windows 10 Secure Until 2027

Microsoft’s Extended Security Updates program provides continued security updates for eligible Windows 10 PCs until at least October 2027. PCs that aren’t enrolled in ESU no longer receive regular security updates following the end of Windows 10 support in October 2025.

If you’re still using Windows 10 and haven’t enrolled in ESU, doing so is necessary to continue receiving important security patches such as KB5120249.