CVE-2026-62772: Windows Container Isolation FS Filter Driver (unionfs.sys) Elevation of Privilege Vulnerability

Overview

Severity

High (CVSS 7.8)

CVSS Vector

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

Category

Elevation of Privilege

Exploit Status

Not Exploited

Exploitation Likelihood

Unlikely

Patch Tuesday

2026-Aug

Released

2026-08-11

Description

Heap-based buffer overflow in Windows Container Isolation FS Filter Driver (unionfs.sys) allows an authorized attacker to elevate privileges locally.

FAQ

What privileges could be gained by an attacker who successfully exploited this vulnerability? An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.

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.