---
id: CVE-2026-72971
title: >-
  Windows Container Isolation FS Filter Driver (unionfs.sys) Tampering
  Vulnerability
summary: >-
  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.
severity: medium
cvss: 5.5
cvssVector: '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'
cvssSource: cna
cwe:
  - CWE-59
vendor: Microsoft
product: Windows 11 version 26H1
affected:
  - windows_11_version_26h1 >= 10.0.28000.0 < 10.0.28000.2704
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-08-11T19:20:18.522655Z'
published: '2026-08-11'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T19:37:27.275Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-72971'
references:
  - url: 'https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-72971'
    label: >-
      Windows Container Isolation FS Filter Driver (unionfs.sys) Tampering
      Vulnerability
tags:
  - cve.org
epss: 0.00364
epssPercentile: 0.27522
ingestedAt: '2026-09-08T19:08:49.657Z'
---

## Overview

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

- `windows_11_version_26h1 >= 10.0.28000.0 < 10.0.28000.2704`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.