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)

KB5123303: what it fixes and who gets it

KB5123303 is a security update from Microsoft's August 2026 release for Windows Server 2022.

Microsoft data read
3CVEs fixed
1rated Critical
0already exploited
Yesrestart required

Should you install it?

Yes. It closes holes Microsoft rates Critical, the most serious rating it uses. 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 KB5123303

CVETypeCVSSSeverity
CVE-2026-66799Windows Key Guard Elevation of Privilege VulnerabilityElevation of Privilege7.8Critical
CVE-2026-6726MITRE: CVE-2026-6726 TPM 2.0 Improper Object Slot ReuseSpoofing7.9Important
CVE-2026-6727MITRE: CVE-2026-6727 TPM 2.0 RSA OAEP Timing Side-Channel VulnerabilityInformation Disclosure5.9Important

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