CVE-2026-83991 Windows Cloud Files Mini Filter Driver Tampering Vulnerability
An authorized local attacker can tamper with data due to missing authentication in the Windows Cloud Files Mini Filter Driver.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-83991?
CVE-2026-83991 is a medium-severity missing authorization vulnerability in Microsoft Windows 10 1809, published on 8 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Missing authentication for critical function in Windows Cloud Files Mini Filter Driver allows an authorized attacker to perform tampering locally.
Weakness: CWE-306
Which versions are affected by CVE-2026-83991?
It affects 10 products.
Products include Microsoft Windows 10 1809, Microsoft Windows 10 21h2, Microsoft Windows 10 22h2, Microsoft Windows 11 23h2, Microsoft Windows 11 24h2, Microsoft Windows 11 25h2 and 4 more.
How do I fix CVE-2026-83991?
No fix has been published for CVE-2026-83991 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-83991 being exploited?
There is no known exploitation of CVE-2026-83991 in the wild and no public exploit code.
Public exploit code: 2 proofs of concept on GitHub.
Other vulnerabilities in Microsoft Windows 10 1809
- CVE-2024-29988 Microsoft SmartScreen Prompt Security Feature Bypass
- CVE-2024-21412 Microsoft Windows Internet Shortcut Files Security Feature Bypass
- CVE-2025-62221 Microsoft Windows Use After Free
- CVE-2025-30400 Microsoft Windows DWM Core Library Use-After-Free
- CVE-2024-21338 Microsoft Windows Kernel Exposed IOCTL with Insufficient Access Control
Sources
Also known as GHSA-6xxg-24pf-j6jx.