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Microsoft Security Response CenterCVE-2026-72971

Windows Container Isolation FS Filter Driver (unionfs.sys) Tampering Vulnerability

HighVendor CVSS 5.5 / 10 1 CVE Published Aug 11, 2026 at 7:00 AM UTC
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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.

Products covered

  • Windows 11 version 26H1 for x64-based Systems

  • Windows 11 Version 26H1 for ARM64-based Systems

Remediation

Install KB5121000.

Vendor-listed fixes

  • 10.0.28000.2704

CVEs in this advisory 1

CVE-2026-72971
Update history

What changed in later vendor updates

SecurityAlert records field-level changes from the point we begin following a bulletin. Earlier vendor changes may not have a field-by-field record.

    • The vendor changed its remediation guidance.

Updates

  1. Published by Microsoft Security Response Center

    The publication date reported by the vendor.

  2. Added to SecurityAlert

    We collected the advisory from the official source.

  3. Confirmed at the source

    Our collector saw this advisory during a later source check.

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