Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Local-only attack requiring a low-privilege session to plant symlinks; no confidentiality loss, no scope change, pure integrity impact on the vulnerable system.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Lifecycle Timeline
3DescriptionCVE.org
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.
AnalysisAI
Symlink-following in the Windows Container Isolation FS Filter Driver (unionfs.sys) enables a locally authenticated attacker with low privileges to tamper with files outside the expected isolation boundary. Affected systems run Windows 11 version 26H1 builds prior to 10.0.28000.2704. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a locally authenticated session with at least low-privilege (standard user) rights on the target Windows 11 26H1 system. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 base score of 5.5 (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N) accurately reflects a moderate local tampering risk: attack complexity is low, but exploitation is confined to the local machine and requires at least a low-privilege authenticated session. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Apply the vendor-released patch that brings Windows 11 26H1 to build 10.0.28000.2704 or later via Windows Update or WSUS; this is the only confirmed fix per EUVD-2026-56603 and the Microsoft Security Response Center advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-72971. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-59 – Improper Link Resolution Before File Access
View allSame technique Information Disclosure
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External POC / Exploit Code
Leaving vuln.today
EUVD-2026-56603
GHSA-mq4h-r45f-27gp