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)

KB5122878: what it fixes and who gets it

KB5122878 is a security update from Microsoft's September 2026 release for Windows 10 Version 21H2, Windows 10 Version 22H2.

Microsoft data read
568CVEs fixed
48rated 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.

Known issues after KB5122878

USB audio devices might fail to start or produce no sound
MitigatedWindows 11 26H2, Windows 11 26H1, Windows 11 25H2, Windows 11 24H2, Windows 11 23H2, Windows 10 22H2updated Sep 29, 2026

Some USB Audio Class 1.0 devices display Code 10 or fail in multichannel audio modes after installing the Sept. 8 update

Remote Desktop Services might stop responding after Sept. 2026 security update
ResolvedWindows 11 26H1, Windows 11 25H2, Windows 11 24H2, Windows 11 23H2, Windows 10 22H2fixed by KB5129194updated Sep 17, 2026

Some Windows devices with Remote Desktop enabled might experience Remote Desktop Services (RDS) instability.

Host folder shares might be unavailable in Hyper-V-based Linux VMs
ResolvedWindows 11 26H1, Windows 11 25H2, Windows 11 24H2, Windows 11 23H2, Windows 10 22H2fixed by KB5129194updated Sep 14, 2026

Plan9 host folder shares might not appear in the guest environment after installing the September 2026 security update.

From Microsoft's Windows release health pages, read hourly. Titles and summaries are Microsoft's.

Security fixes in KB5122878

CVETypeCVSSSeverity
CVE-2026-85880Windows Advanced Local Procedure Call (ALPC) Elevation of Privilege VulnerabilityElevation of Privilege7.8ExploitedImportant
CVE-2026-69579Windows Message Queuing Remote Code Execution VulnerabilityRemote Code Execution9.8Critical
CVE-2026-69590Windows Routing and Remote Access Service (RRAS) Remote Code Execution VulnerabilityRemote Code Execution9.8Critical
CVE-2026-69769Windows HTTP Print Provider Remote Code Execution VulnerabilityRemote Code Execution9.8Critical
CVE-2026-69829Windows Shell Remote Code Execution VulnerabilityRemote Code Execution9.8Critical
CVE-2026-70296Windows Imaging Component Remote Code Execution VulnerabilityRemote Code Execution9.8Critical
CVE-2026-72982Windows Netlogon Remote Code Execution VulnerabilityRemote Code Execution9.8Critical
CVE-2026-72983Internet Connection Sharing (ICS) Remote Code Execution VulnerabilityRemote Code Execution9.8Critical
CVE-2026-73009Windows Secure Socket Tunneling Protocol (SSTP) Remote Code Execution VulnerabilityRemote Code Execution9.8Critical
CVE-2026-77493Windows Graphics Component Remote Code Execution VulnerabilityRemote Code Execution9.8Critical
CVE-2026-69499Windows Imaging Component Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-69518Windows Remote Desktop Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-69601Microsoft Windows Media Foundation Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-69603Windows Hyper-V Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-69676Windows Kerberos Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-69784Windows Hello Elevation of Privilege VulnerabilityElevation of Privilege8.8Critical
CVE-2026-69860Windows Imaging Component Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-70203Windows Media Player Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-70586Windows Paint Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-72950Windows Routing and Remote Access Service (RRAS) Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-72959Windows Routing and Remote Access Service (RRAS) Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-72960Windows Media Player Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-72986Graphic Fonts Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-73006DirectWrite Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-73013Windows Imaging Component Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-73018Graphic Fonts Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-73023Windows Imaging Component Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-77495Windows Imaging Component Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-77504Microsoft Office Word Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-81955Windows Graphics Component Remote Code Execution VulnerabilityRemote Code Execution8.8Critical
CVE-2026-69820Windows Hello Elevation of Privilege VulnerabilityElevation of Privilege8.2Critical
CVE-2026-69846Windows Secure Kernel Mode Elevation of Privilege VulnerabilityElevation of Privilege8.2Critical
CVE-2026-69874Windows ALPC Elevation of Privilege VulnerabilityElevation of Privilege8.2Critical
CVE-2026-69906Windows Secure Kernel Mode Elevation of Privilege VulnerabilityElevation of Privilege8.2Critical
CVE-2026-72961Windows Hyper-V Elevation of Privilege VulnerabilityElevation of Privilege8.2Critical
CVE-2026-72962Windows USB Video Driver Elevation of Privilege VulnerabilityElevation of Privilege8.2Critical
CVE-2026-81354Windows Hello Elevation of Privilege VulnerabilityElevation of Privilege8.2Critical
CVE-2026-72981IP Helper Remote Code Execution VulnerabilityRemote Code Execution8.1Critical
CVE-2026-78449Windows Reliable Multicast Transport Driver (RMCAST) Remote Code Execution VulnerabilityRemote Code Execution8.1Critical
CVE-2026-69725Windows Hello Elevation of Privilege VulnerabilityElevation of Privilege7.8Critical
CVE-2026-69799Windows Hello Elevation of Privilege VulnerabilityElevation of Privilege7.8Critical
CVE-2026-69864Windows Hello Elevation of Privilege VulnerabilityElevation of Privilege7.8Critical
CVE-2026-69710Windows Hello Elevation of Privilege VulnerabilityElevation of Privilege7.5Critical
CVE-2026-69852Windows Routing and Remote Access Service (RRAS) Remote Code Execution VulnerabilityRemote Code Execution7.5Critical
CVE-2026-69890Windows Virtual Trusted Platform Module Elevation of Privilege VulnerabilityElevation of Privilege7.5Critical
CVE-2026-73017Graphics Kernel Remote Code Execution VulnerabilityRemote Code Execution7.5Critical
CVE-2026-81355Virtual Hard Disk (VHD) Miniport Driver Remote Code Execution VulnerabilityRemote Code Execution7.5Critical
CVE-2026-69501Windows Secure Kernel Mode Elevation of Privilege VulnerabilityElevation of Privilege7.0Critical
CVE-2026-72980Windows Hello Security Feature Bypass VulnerabilitySecurity Feature Bypass4.4Critical
CVE-2026-68839Windows USB Mass Storage Class Driver Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-69276Microsoft UxTheme Library (uxtheme.dll) Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-69408Microsoft Windows Media Foundation Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-69431Telnet Client Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-69463Windows NTFS Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-69491Microsoft DirectMusic Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-69493Windows Event Logging Service Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-69496Windows Compressed Folder Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-69525Remote Desktop Services Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-69586Microsoft Windows PDF Remote Code Execution VulnerabilityRemote Code Execution9.8Important
CVE-2026-69715Windows Direct Show Remote Code Execution VulnerabilityRemote Code Execution9.8Important
Showing the 60 most severe of 568. The full list is in Microsoft's Security Update Guide.

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