Microsoft ships Windows 10 KB5099539 as record 570-flaw Patch Tuesday lands
The July 2026 update patches two actively exploited zero-days and quietly extends free security fixes for home users into 2027.
Key points
- Microsoft released the Windows 10 KB5099539 update on July 14, 2026, part of a Patch Tuesday fixing 570 vulnerabilities.
- The July 2026 batch includes two flaws already being exploited by attackers and one publicly disclosed zero-day.
- Microsoft extended its free Extended Security Updates programme for home users, giving enrolled Windows 10 devices patches until October 12, 2027.
- After installing, Windows 10 moves to build 19045.7548 and Windows 10 Enterprise LTSC 2021 to build 19044.7548.
- A networking change may break older apps that rely on unregistered third-party TDI transports.
Microsoft released KB5099539 on July 14, 2026, a Windows 10 security update bundled with the largest Patch Tuesday on record: 570 vulnerabilities fixed in a single month. As we reported the same day, an AI system Microsoft is using to hunt bugs in Windows is partly responsible for the inflated count.
A vulnerability is a flaw in software that attackers can abuse to break in or take control of a machine. Three of this month's flaws are zero-days, meaning they were exploited or publicly known before Microsoft had a fix. Two were already being used in real attacks.
Do I still get updates if I'm on Windows 10?
Yes, for now. Microsoft officially ended free support for Windows 10 last year, but it extended its Extended Security Updates programme for home users by another year. Enrolled devices will keep receiving patches until October 12, 2027.
That matters because hundreds of millions of PCs still run Windows 10. Without patches, each new flaw becomes a permanent open door.
If you're on Windows 10 Enterprise LTSC or enrolled in the ESU programme, the update arrives through the normal route: Settings, then Windows Update, then Check for Updates. After it installs, your build number will read 19045.7548, or 19044.7548 on Enterprise LTSC 2021.
What is actually in this update?
Microsoft isn't adding new features to Windows 10, so KB5099539 is almost entirely security fixes and bug repairs.
The smaller fixes address problems introduced by June's update. One broke certain older applications that use a Windows component called OLE Automation to pass data between programs. Another caused the OneDrive shortcut in File Explorer to stop working when File Explorer ran as an administrator. A third made the Recycle Bin display an internal file name rather than the original when you permanently deleted a file.
There's also a Secure Boot change: Windows Security will now show a live status for Secure Boot, and Microsoft is widening the rollout of new Secure Boot certificates to more machines.
Remote Desktop gets a security tightening too. Microsoft is moving away from the old SHA-1 signing method toward SHA-256. IT administrators are told to migrate as soon as possible.
Should I be worried about anything breaking?
Mostly no, but one catch is worth flagging.
Microsoft has hardened a piece of networking plumbing called TDI. Some very old third-party networking add-ons that never properly registered themselves with Windows will stop working after this update. Modern apps aren't affected.
If a business app loses network access after patching, an administrator can check Windows Event Viewer for an entry marked AFD Event ID 16003. That entry names the offending driver.
For home users, there's nothing to do beyond installing the update. Two of the fixed flaws are being exploited right now, so delaying is the risky option. Turn the machine on, let Windows Update run, reboot when asked.
