Microsoft March 2026 Patch Tuesday: Fixes for 2 Zero-Day Vulnerabilities

Key Takeaways

1. Microsoft’s March 2026 Patch Tuesday addresses 79 vulnerabilities, including two zero-days and three critical issues.
2. Updates KB5079473 and KB5078883 for Windows 11 improve security and reliability, while KB5078885 for Windows 10 also combines security fixes with quality improvements.
3. Security vulnerabilities in Microsoft Office, particularly related to remote code execution, have been patched this month.
4. The updates enhance features like Secure Boot certificate targeting and File Explorer reliability, with no known issues reported.
5. Windows 10 users are especially impacted, as this update is crucial following the end of mainstream support on October 14, 2025.

Microsoft’s Patch Tuesday on March 10, 2026, brings important fixes for a total of 79 vulnerabilities. This includes two zero-days that were made public and three Critical weaknesses. As per BleepingComputer’s summary, the zero-days include CVE-2026-21262 in SQL Server and CVE-2026-26127 in .NET. Additionally, this month’s update also resolves two remote-code-execution issues in Microsoft Office that can be activated through the preview pane.

Windows Update Details

On the Windows front, Microsoft has released KB5079473 for Windows 11 versions 25H2 and 24H2, updating those builds to OS Builds 26200.8037 and 26100.8037, respectively. For Windows 11 version 23H2, KB5078883 is now available, bringing it to OS Build 22631.6783. Windows 10’s versions 22H2 and 21H2 have also received KB5078885, which updates them to OS Builds 19045.7058 and 19044.7058.

Microsoft states that KB5079473 for Windows 11 versions 25H2 and 24H2 contains the latest security fixes along with non-security updates from the previous month’s preview release. The support documentation mentions enhanced Secure Boot certificate targeting, improved reliability in File Explorer search across multiple drives or “This PC,” better handling of COM allowlisting policies in Windows Defender Application Control, and a clearer trust warning in Windows System Image Manager. The company also indicates that no issues have been reported with this update.

Specifics for Windows 11 and 10

For Windows 11 version 23H2, KB5078883 addresses security vulnerabilities and includes quality fixes from February. These enhancements feature broader targeting for new Secure Boot certificates, two new PowerShell options related to Secure Boot, improved File History reliability for certain character sets, enhanced GPU stability during shutdowns and heavy graphics tasks, and the same trusted-catalog warning dialog in Windows System Image Manager. According to Microsoft’s support page, they are not aware of any problems associated with KB5078883.

Similarly, Windows 10’s KB5078885 combines March’s security fixes with some quality improvements. Microsoft emphasizes a trusted-source warning for catalog file selection in Windows System Image Manager, fixes for File History backups concerning specific Chinese and Private Use Area character names, better GPU stability, and broader targeting for devices that can automatically receive new Secure Boot certificates. Microsoft claims there are no known issues with this update as well.

Focus on Vulnerabilities

The main focus remains on the vulnerabilities rather than the feature updates. In addition to the two public zero-days, BleepingComputer reveals that Microsoft has also patched two flaws in Office that could be exploited through the preview pane, and an Excel issue that could be used to extract data via Copilot Agent mode. This makes March’s Patch Tuesday more significant than a typical cumulative update, even if Microsoft’s release notes are somewhat sparse in terms of user-facing changes.

For Windows 10 users, this update comes after the end of mainstream support for Windows 10 on October 14, 2025. Microsoft has stated that PCs can continue to operate, but standard technical support, feature updates, and security updates will not be available outside of the Extended Security Updates path. This is why March’s Windows 10 security package is especially important for systems that are still being maintained under that post-EOS route.

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