CVE-2026-72971: Windows Container Isolation FS Filter Driver (unionfs.sys) Tampering Vulnerability

Overview

Severity

Medium (CVSS 5.5)

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N/E:U/RL:O/RC:C

Category

Tampering

Exploit Status

Not Exploited

Exploitation Likelihood

Unlikely

Publicly Disclosed

Yes

Patch Tuesday

2026-Aug

Released

2026-08-11

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.

Affected Products (2)

Windows

• Windows 11 version 26H1 for x64-based Systems
• Windows 11 Version 26H1 for ARM64-based Systems

Security Updates (1)

• 5121000

Acknowledgments

yhw & txz

Revision History

• 2026-08-11: Information published.