Auth bypass in Microsoft Windows 10 Version 1809
CVE-2026-83991
Missing authentication for critical function in Windows Cloud Files Mini Filter Driver allows an authorized attacker to perform tampering locally.
Vulnerability class: Broken Authentication
CVSS v3 metric
CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N.
Affected products
- Microsoft Windows 10 Version 1809
- Microsoft Windows 10 Version 21h2
- Microsoft Windows 10 Version 22h2
- Microsoft Windows 11 Version 23h2
- Microsoft Windows 11 Version 24h2
- Microsoft Windows 11 Version 25h2
- Microsoft Windows 11 Version 26h1
- Microsoft Windows Server 2019
- Microsoft Windows Server 2019 (Server Core Installation)
- Microsoft Windows Server 2022
Weakness classification (CWE)
Public proof-of-concept exploits
References
- secure@microsoft.com (vendor-advisory, patch)
Frequently asked questions
- What is CVE-2026-83991?
- CVE-2026-83991 is a medium-severity vulnerability in Microsoft Windows 10 Version 1809, classified under Missing Authentication for Critical Function. CVSS score: 5.5/10. Published 2026-09-08.
- How severe is CVE-2026-83991?
- Medium severity. CVSS v3 base score is 5.5 out of 10.
- Is CVE-2026-83991 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.