3 OctRestore deleted or older files in OneDrive3 OctRun the Windows Update troubleshooter3 OctWindows File Recovery: recover permanently deleted files with winfr3 OctHow to update drivers in Windows 11 and 10 (roll back, reinstall)3 OctDisable Fast Startup in Windows 11 and 103 OctUse System Restore in Windows 11 and Windows 103 OctHow to stop apps from opening on startup3 OctRun Startup Repair in Windows 11 (fix the Automatic Repair loop)

KB5099538: what it fixes and who gets it

KB5099538 is a security update from Microsoft's July 2026 release for Windows 10 Version 1809.

Microsoft data read
311CVEs fixed
27rated Critical
1already exploited
Yesrestart required

Should you install it?

Yes, and soon: it closes a hole that was already being used in real attacks before the fix was released. Windows Update installs it automatically on supported home PCs.

If the installation fails or the PC misbehaves afterwards, note the exact error code first: the fix depends on it. Our update troubleshooting guides are linked on this page.

Security fixes in KB5099538

CVETypeCVSSSeverity
CVE-2026-56155Active Directory Federation Services Elevation of Privilege VulnerabilityElevation of Privilege7.8ExploitedImportant
CVE-2026-57092Microsoft Windows VMSwitch Elevation of Privilege VulnerabilityElevation of Privilege9.9Critical
CVE-2026-50518Windows DHCP Server Remote Code Execution VulnerabilityRemote Code Execution9.8Critical
CVE-2026-56159DHCP Server Service Remote Code Execution VulnerabilityRemote Code Execution9.8Critical
CVE-2026-56188Windows Server Network driver Remote Code Execution VulnerabilityRemote Code Execution9.8Critical
CVE-2026-50380Windows GDI+ Remote Code Execution VulnerabilityRemote Code Execution9.6Critical
CVE-2026-48564DHCP Server Service Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-50370DHCP Server Service Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-50382DirectX Graphics Kernel Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-50444Windows Server Update Service (WSUS) Elevation of Privilege VulnerabilityElevation of Privilege8.8Critical
CVE-2026-50474Remote Desktop Client Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-54121Active Directory Certificate Services Elevation of Privilege VulnerabilityElevation of Privilege8.8Critical
CVE-2026-54982Windows Reliable Multicast Transport Driver (RMCAST) Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-54999Windows TCP/IP Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-57087Microsoft Windows Media Foundation Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-57090Microsoft Windows Media Foundation Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-57094Microsoft Windows Media Foundation Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-58608Windows Print Spooler Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-54128Windows DHCP Client Remote Code Execution VulnerabilityRemote Code Execution8.4Critical
CVE-2026-54992Microsoft Message Queuing Queue Manager Remote Code Execution VulnerabilityRemote Code Execution8.4Critical
CVE-2026-50680Windows Hyper-V Elevation of Privilege VulnerabilityElevation of Privilege8.2Critical
CVE-2026-49164Windows Active Directory Domain Services Remote Code Execution VulnerabilityRemote Code Execution8.1Critical
CVE-2026-50694Windows Secure Socket Tunneling Protocol (SSTP) Remote Code Execution VulnerabilityRemote Code Execution8.1Critical
CVE-2026-54995Windows Reliable Multicast Transport Driver (RMCAST) Remote Code Execution VulnerabilityRemote Code Execution8.1Critical
CVE-2026-42982Windows Secure Kernel Mode Elevation of Privilege VulnerabilityElevation of Privilege7.8Critical
CVE-2026-49796Windows GDI+ Remote Code Execution VulnerabilityRemote Code Execution7.8Critical
CVE-2026-50655Microsoft Windows Media Foundation Remote Code Execution VulnerabilityRemote Code Execution7.8Critical
CVE-2026-56189Microsoft Windows Media Foundation Remote Code Execution VulnerabilityRemote Code Execution7.8Critical
CVE-2026-42990SQL Server ODBC driver Elevation of Privilege VulnerabilityRemote Code Execution9.8Important
CVE-2026-49172Windows FTP Service Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-50447Windows Message Queuing Service (MSMQ) Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-56190Remote Desktop Protocol Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-49798Windows Kernel Elevation of Privilege VulnerabilityElevation of Privilege9.3Important
CVE-2026-49178Windows Active Directory Domain Services Remote Code Execution VulnerabilityRemote Code Execution8.8Important
CVE-2026-49795Windows Kernel Elevation of Privilege VulnerabilityElevation of Privilege8.8Important
CVE-2026-50369Windows Remote Desktop Services Elevation of Privilege VulnerabilityElevation of Privilege8.8Important
CVE-2026-50477Windows Kernel Elevation of Privilege VulnerabilityElevation of Privilege8.8Important
CVE-2026-50489Win32k Elevation of Privilege VulnerabilityElevation of Privilege8.8Important
CVE-2026-50666Windows Remote Access Elevation of Privilege VulnerabilityElevation of Privilege8.8Important
CVE-2026-50670Windows Win32k Elevation of Privilege VulnerabilityElevation of Privilege8.8Important
CVE-2026-50692Desktop Window Manager Elevation of Privilege VulnerabilityElevation of Privilege8.8Important
CVE-2026-54107Windows Win32k Elevation of Privilege VulnerabilityElevation of Privilege8.8Important
CVE-2026-56194Windows NFS Server Elevation of Privilege VulnerabilityElevation of Privilege8.8Important
CVE-2026-56647Windows Remote Access Service Infrastructure Elevation of Privilege VulnerabilityElevation of Privilege8.8Important
CVE-2026-58534Windows Input Method Editor (IME) Elevation of Privilege VulnerabilityElevation of Privilege8.8Important
CVE-2026-58594Remote Desktop Client Remote Code Execution VulnerabilityRemote Code Execution8.8Important
CVE-2026-49184Windows NTFS Remote Code Execution VulnerabilityRemote Code Execution8.4Important
CVE-2026-54122Windows GDI+ Remote Code Execution VulnerabilityRemote Code Execution8.4Important
CVE-2026-50429Windows Kernel Information Disclosure VulnerabilityInformation Disclosure8.2Important
CVE-2026-42900Microsoft Windows App Store Elevation of Privilege VulnerabilityElevation of Privilege8.1Important
CVE-2026-50439Microsoft Message Queuing Queue Manager Remote Code Execution VulnerabilityRemote Code Execution8.1Important
CVE-2026-50460Windows Runtime Elevation of Privilege VulnerabilityElevation of Privilege8.1Important
CVE-2026-50686Windows OLE Remote Code Execution VulnerabilityRemote Code Execution8.1Important
CVE-2026-56186Windows Secure Channel Information Disclosure VulnerabilityInformation Disclosure8.1Important
CVE-2026-40400Windows PowerShell Remote Code Execution VulnerabilityRemote Code Execution8.0Important
CVE-2026-42975Windows Bluetooth Port Driver Remote Code ExecutionRemote Code Execution8.0Important
CVE-2026-50365Remote Access Management service/API (RPC server) Elevation of Privilege VulnerabilityElevation of Privilege8.0Important
CVE-2026-50502Windows Event Logging Service Remote Code Execution VulnerabilityRemote Code Execution8.0Important
CVE-2026-50683Windows DHCP Client Elevation of Privilege VulnerabilityElevation of Privilege8.0Important
CVE-2026-49170Windows StateRepository API Server file Elevation of Privilege VulnerabilityElevation of Privilege7.8Important
Showing the 60 most severe of 311. The full list is in Microsoft's Security Update Guide.

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