Microsoft releases Windows 10 KB5099539 extended security update
Microsoft released the Windows 10 KB5099539 extended security update, which includes the July 2026 Patch Tuesday fixes addressing 570 vulnerabilities, including two exploited and one publicly disclosed zero-day. This update is part of the extended security updates (ESU) program for Windows 10, now extended to October 12, 2027, for enrolled devices. It primarily contains security patches and bug fixes without new features, updating Windows 10 to build 19045.7548 and Windows 10 Enterprise LTSC 2021 to build 19044.7548. Notable fixes include resolving issues in OLE Automation, File Explorer, Recycle Bin, input hotkey behavior, Secure Boot status reporting, networking transport registration, and Remote Desktop security enhancements. Some legacy applications using unregistered TDI transports may stop working due to new security hardening. Microsoft recommends migrating to SHA-256 for RDP certificate thumbprints to avoid future disruptions.
AI Analysis
Technical Summary
The Windows 10 KB5099539 update is an extended security update released by Microsoft as part of the July 2026 Patch Tuesday, addressing 570 vulnerabilities including two exploited and one publicly disclosed zero-day. It updates Windows 10 and Windows 10 Enterprise LTSC 2021 to specific builds and includes fixes for known issues in OLE Automation, File Explorer, Recycle Bin, input hotkeys, Secure Boot, networking TDI transport registration, and Remote Desktop security. The update enforces stricter security requirements such as TDI transport registration, which may impact legacy applications. It also enhances Secure Boot status reporting and introduces support for SHA-2 certificate thumbprints in RDP. The update is available to devices enrolled in the Extended Security Updates program, which Microsoft extended through October 12, 2027.
Potential Impact
This update addresses a large number of vulnerabilities (570), including actively exploited and publicly disclosed zero-day flaws, thereby reducing the attack surface on Windows 10 systems enrolled in the ESU program. The security hardening of TDI transport registration may cause compatibility issues with legacy applications using unregistered third-party TDI transports. The update improves Secure Boot security and Remote Desktop security by encouraging migration to stronger certificate algorithms. Failure to apply this update may leave systems vulnerable to known exploits and security issues fixed by this patch.
Mitigation Recommendations
A security update (KB5099539) is available and should be installed by Windows 10 Enterprise LTSC and ESU-enrolled devices via Windows Update. Microsoft manages remediation for this update through the ESU program, which has been extended until October 12, 2027. IT administrators should verify application compatibility, especially for legacy software using unregistered TDI transports, by checking Event Viewer for Event ID 16003. Migration to SHA-256 certificate thumbprints for RDP is recommended to avoid future disruptions. No additional mitigation actions are indicated beyond applying the update and following Microsoft's guidance.
Microsoft releases Windows 10 KB5099539 extended security update
Description
Microsoft released the Windows 10 KB5099539 extended security update, which includes the July 2026 Patch Tuesday fixes addressing 570 vulnerabilities, including two exploited and one publicly disclosed zero-day. This update is part of the extended security updates (ESU) program for Windows 10, now extended to October 12, 2027, for enrolled devices. It primarily contains security patches and bug fixes without new features, updating Windows 10 to build 19045.7548 and Windows 10 Enterprise LTSC 2021 to build 19044.7548. Notable fixes include resolving issues in OLE Automation, File Explorer, Recycle Bin, input hotkey behavior, Secure Boot status reporting, networking transport registration, and Remote Desktop security enhancements. Some legacy applications using unregistered TDI transports may stop working due to new security hardening. Microsoft recommends migrating to SHA-256 for RDP certificate thumbprints to avoid future disruptions.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Windows 10 KB5099539 update is an extended security update released by Microsoft as part of the July 2026 Patch Tuesday, addressing 570 vulnerabilities including two exploited and one publicly disclosed zero-day. It updates Windows 10 and Windows 10 Enterprise LTSC 2021 to specific builds and includes fixes for known issues in OLE Automation, File Explorer, Recycle Bin, input hotkeys, Secure Boot, networking TDI transport registration, and Remote Desktop security. The update enforces stricter security requirements such as TDI transport registration, which may impact legacy applications. It also enhances Secure Boot status reporting and introduces support for SHA-2 certificate thumbprints in RDP. The update is available to devices enrolled in the Extended Security Updates program, which Microsoft extended through October 12, 2027.
Potential Impact
This update addresses a large number of vulnerabilities (570), including actively exploited and publicly disclosed zero-day flaws, thereby reducing the attack surface on Windows 10 systems enrolled in the ESU program. The security hardening of TDI transport registration may cause compatibility issues with legacy applications using unregistered third-party TDI transports. The update improves Secure Boot security and Remote Desktop security by encouraging migration to stronger certificate algorithms. Failure to apply this update may leave systems vulnerable to known exploits and security issues fixed by this patch.
Mitigation Recommendations
A security update (KB5099539) is available and should be installed by Windows 10 Enterprise LTSC and ESU-enrolled devices via Windows Update. Microsoft manages remediation for this update through the ESU program, which has been extended until October 12, 2027. IT administrators should verify application compatibility, especially for legacy software using unregistered TDI transports, by checking Event Viewer for Event ID 16003. Migration to SHA-256 certificate thumbprints for RDP is recommended to avoid future disruptions. No additional mitigation actions are indicated beyond applying the update and following Microsoft's guidance.
Technical Details
- Article Source
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Threat ID: 6a5687db68715ace4309665a
Added to database: 07/14/2026, 19:02:51 UTC
Last enriched: 07/14/2026, 19:03:06 UTC
Last updated: 07/15/2026, 04:28:27 UTC
Views: 58
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