Missing Authentication for Critical Function in Microsoft Windows and Windows Server - CVE-2026-83991
Published: September 9, 2026
Vulnerability identifier: #VU148342
CSH Severity: Low
CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-83991
CWE-ID: CWE-306
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to make unauthorized modifications to protected system data.
The vulnerability exists due to missing authentication for critical function in Windows Cloud Files Mini Filter Driver when invoking critical functions. A local user can invoke critical functions without authentication to make unauthorized modifications to protected system data.
Affected software
Microsoft Windows
Windows Server
Windows Server
How to mitigate CVE-2026-83991
Install security update from vendor's website.
Microsoft Windows - addressed in versions 10 21H2 10.0.19044.7725, 10 22H2 10.0.19045.7725, 10 1809 10.0.17763.9245, 11 23H2 10.0.22631.7582, 11 24H2 10.0.26100.9445, 11 25H2 10.0.26200.9445, 11 26H1 10.0.28000.2954
Windows Server - addressed in versions 2019 10.0.17763.9245, 2022 10.0.20348.5622, 2025 10.0.26100.33438
Windows Server - addressed in versions 2019 10.0.17763.9245, 2022 10.0.20348.5622, 2025 10.0.26100.33438