CVE-2026-97790 — Windows Container Isolation FS Filter Driver (unionfs.sys) Tampering Vulnerability

Executive 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.

Overview

5.5

CVSS MEDIUM

Important

MS Severity

Not Exploited

MS Exploit Status

Less Likely

MS Exploit Likelihood

Category Tampering

Weakness CWE-59: Improper Link Resolution Before File Access ('Link Following')

Released Oct 13 2026

Last Updated Oct 13 2026

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

CVSS Vector

ATTACK VECTOR

Local

ATTACK COMPLEXITY

Low

PRIVILEGES REQUIRED

Low

USER INTERACTION

None

SCOPE

Unchanged

CONFIDENTIALITY

None

INTEGRITY

High

AVAILABILITY

None

EXPLOIT CODE MATURITY

Unproven

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 4.8

EPSS Score

No EPSS score available for this CVE.

View on FIRST.org

Affected Products

12 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 11 Version 24H2 for ARM64-based Systems	`5127648 (Security Update)`	Important	Tampering	Yes
Windows 11 Version 24H2 for x64-based Systems	`5127648 (Security Update)`	Important	Tampering	Yes
Windows 11 Version 25H2 for ARM64-based Systems	`5127648 (Security Update)`	Important	Tampering	Yes
Windows 11 Version 25H2 for x64-based Systems	`5127648 (Security Update)`	Important	Tampering	Yes
Windows 11 Version 26H1 for ARM64-based Systems	`5127646 (Security Update)`	Important	Tampering	Yes
Windows 11 version 26H1 for x64-based Systems	`5127646 (Security Update)`	Important	Tampering	Yes
Windows 11 Version 26H2 for ARM64-based Systems	`5127648 (Security Update)`	Important	Tampering	Yes
Windows 11 Version 26H2 for x64-based Systems	`5127648 (Security Update)`	Important	Tampering	Yes
Windows Server 2022	`5126655 (Security Update)`	Important	Tampering	Yes
Windows Server 2022 (Server Core installation)	`5126655 (Security Update)`	Important	Tampering	Yes
Windows Server 2025	`5126646 (Security Update)`	Important	Tampering	Yes
Windows Server 2025 (Server Core installation)	`5126646 (Security Update)`	Important	Tampering	Yes

Patches

4 patches

Article	Type	Restart
`5127648`	Security Update	Yes
`5127646`	Security Update	Yes
`5126655`	Security Update	Yes
`5126646`	Security Update	Yes

Exploits & PoC

No public exploit or PoC has been linked for this CVE yet. When available, references are sourced from public repositories and may be unverified or non-functional — review carefully before use.

Detection Rules

No public Sigma or Nuclei detection rule has been mapped to this CVE yet. Coverage is concentrated on exploited / high-profile vulnerabilities; check SigmaHQ for updates.

Acknowledgments

yhw

References

MSRC Advisory MITRE NVD