CVE-2026-72971 Windows Container Isolation FS Filter Driver (unionfs.sys) Tampering Vulnerability
An authorized local attacker can tamper with files via improper link resolution in the Windows Container Isolation FS 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-2026-72971?
CVE-2026-72971 is a medium-severity path traversal vulnerability in Microsoft Windows 11 26h1, published on 11 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Improper link resolution before file access ('link following') in Windows Container Isolation FS Filter Driver (unionfs.sys) allows an authorized attacker to perform tampering locally.
Weakness: CWE-59
Which versions are affected by CVE-2026-72971?
It affects 1 product.
Products include Microsoft Windows 11 26h1.
How do I fix CVE-2026-72971?
No fix has been published for CVE-2026-72971 yet. Limit exposure of the affected software until one is available.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-72971 being exploited?
There is no known exploitation of CVE-2026-72971 in the wild and no public exploit code.
Other vulnerabilities in Microsoft Windows 11 26h1
- CVE-2026-85921 Windows Secure Kernel Mode Elevation of Privilege Vulnerability
- CVE-2026-83939 Windows Secure Kernel Mode Elevation of Privilege Vulnerability
- CVE-2026-105005 Windows Schannel Remote Code Execution Vulnerability
- CVE-2026-85850 Windows Kernel Elevation of Privilege Vulnerability
- CVE-2026-97803 Windows Kernel Elevation of Privilege Vulnerability
Sources
Also known as GHSA-mq4h-r45f-27gp.