CVE-2026-97790: 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

Less Likely

Patch Tuesday

2026-Oct

Released

2026-10-13

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 (12)

Windows

• Windows Server 2022
• Windows Server 2022 (Server Core installation)
• Windows 11 Version 24H2 for ARM64-based Systems
• Windows 11 Version 24H2 for x64-based Systems
• Windows 11 Version 25H2 for ARM64-based Systems
• Windows 11 Version 25H2 for x64-based Systems
• Windows 11 Version 26H2 for ARM64-based Systems
• Windows 11 Version 26H2 for x64-based Systems
• Windows Server 2025
• Windows Server 2025 (Server Core installation)
• Windows 11 Version 26H1 for ARM64-based Systems
• Windows 11 version 26H1 for x64-based Systems

Security Updates (4)

• 5126655
• 5127648
• 5126646
• 5127646

Acknowledgments

yhw

Revision History

• 2026-10-13: Information published.