Windows 10 KB5099539: What’s Fixed in the July 2026 ESU Update

On Tuesday, July 14, 2026, Microsoft released the July 2026 ESU update for Windows 10: KB5099539. On the menu: fixes for several known bugs, including some introduced with the June 2026 update. Here’s what you need to know.

For context, the July 2026 Patch Tuesday is the largest ever released by Microsoft: 570 vulnerabilities fixed, including 57 critical issues and 3 zero-day flaws (two already exploited, one publicly disclosed). That volume of flaws is no accident, since Microsoft warned a few days earlier that AI would make Patch Tuesday updates bigger. The ESU update is therefore the practical outcome of those statements, and the July 2026 release makes it possible to install security patches for Windows 10.

After installation, Windows 10 22H2 machines move to build 19045.7548, while Windows 10 Enterprise LTSC 2021 (21H2) moves to 19044.7548. The update is available through Windows Update and the Microsoft Update Catalog.

Also check out the July 2026 update for Windows 11.

Microsoft fixes the June fallout

As expected, Microsoft is not delivering any new features on Windows 10. The KB5099539 focuses on fixes, whether for security or bug resolution.

The most anticipated fix is probably the one related to OLE automation, the decades-old mechanism that lets one piece of software control another in the background. For example, your line-of-business app that generates a letter in Word or fills in an Excel workbook without the user opening Office directly. The June 2026 security update broke the mechanism, to the point that Microsoft admitted on June 16 that "some third-party applications might be unable to start Microsoft Office applications or open documents", sometimes without any error message at all. KB5099539 resolves this issue.

Here are some of the other bugs fixed by this update (the first two are known issues):

• File Explorer: the OneDrive shortcut stopped working when File Explorer was launched in administrator mode. This is fixed.
• Recycle Bin: during a permanent delete, the confirmation dialog could display the Recycle Bin’s internal file name instead of the original name.
• Input: Microsoft is changing the behavior of shortcut key unregistration and cleanup. The US vendor warns that in rare cases, some experiences built into Windows could temporarily stop responding to certain keyboard shortcuts. Restarting the affected app usually resolves the issue.

This update fixes issues, and for now, it does not introduce any new ones: Microsoft lists no known issues at the time of publication (which is not always the case).

TDI and RDP: two changes to watch

Through KB5099539, Microsoft has also introduced two changes that may affect enterprise environments.

The first concerns networking. Microsoft now requires registration of Transport Driver Interface (TDI) interfaces. As a result, applications that use sockets over unregistered third-party TDI transports may stop working after this update is installed.

How can you tell whether you are affected by this change? Microsoft provides the procedure: "To determine if you have a TDI transport affected by this change, check the Windows system event logs in Event Viewer > Windows > System. If you find an AFD Event ID: 16003 ‘An unregistered TDI provider (\Driver<Name>) was detected’, then your TDI transport is affected by this change.".

The second change targets Remote Desktop. Microsoft is adding support for SHA-2 certificate fingerprints for approved RDP publishers. SHA-1 is still accepted, but only for backward compatibility, and its removal is planned. The vendor recommends moving to SHA-256 fingerprints (or a stronger algorithm).

The Windows 10 ESU update list

Below is the list of Windows 10 ESU updates released so far.

This article is also an opportunity to remember that Microsoft has quietly extended the free ESU program until October 2027, one year longer than expected for enrolled consumer devices.

Additional resources on the topic to help you out:

• Windows 10 ESU: how do you enroll your PC to get security updates?
• Windows 10 standard support ends on October 14, 2025: what are the consequences?
• How do you move to Windows 10 LTSC without losing your data?

Florian Burnel Co-founder of IT-Connect

Systems and network engineer, co-founder of IT-Connect and Microsoft MVP "Cloud and Datacenter Management". I'd like to share my experience and discoveries through my articles. I'm a generalist with a particular interest in Microsoft solutions and scripting. Enjoy your reading.

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