MSRC-CVE-2026-83586 — Windows Resilient File System (ReFS) Deduplication Service Elevation of Privilege Vulnerability

Summary

Impact: Elevation of Privilege. Microsoft rating: Important. Not known to be exploited — Exploitation Unlikely. Customer action: Required.

Details

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

Security updates
10.0.26100.33650 — https://support.microsoft.com/help/5126646
10.0.26200.9711 — https://support.microsoft.com/help/5127648
10.0.22631.7652 — https://support.microsoft.com/help/5126653
10.0.28000.3231 — https://support.microsoft.com/help/5127646

Vulnerabilities 1

High 7.8

CVE-2026-83586

Windows Resilient File System (ReFS) Deduplication Service Elevation of Privilege Vulnerability

Weak authentication in Windows Resilient File System (ReFS) Deduplication Service allows an authorized attacker to elevate privileges locally.

Microsoft Windows Server 2025 Windows Server 2025 (Server Core installation) Windows 11 Version 24H2 Windows

Oct 13, 2026

Revision history

2026-10-13 #1
Information published.

References

CVE-2026-83586 Windows Resilient File System (ReFS) Deduplication Service Elevation of Privilege Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-83586
Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
Common Vulnerability Scoring System
https://www.first.org/cvss