MSRC-CVE-2026-71338 — Windows Failover Cluster Elevation of Privilege Vulnerability

Summary

Impact: Elevation of Privilege. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. 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.

According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability?
Successful exploitation of this vulnerability requires an attacker to win a race condition.

Security updates
10.0.17763.9245 — https://support.microsoft.com/help/5122876
10.0.20348.5622 — https://support.microsoft.com/help/5122882
10.0.26100.33438 — https://support.microsoft.com/help/5122871
10.0.14393.9512 — https://support.microsoft.com/help/5123099
6.2.9200.26349 — https://support.microsoft.com/help/5123065
6.3.9600.23398 — https://support.microsoft.com/help/5123066

Vulnerabilities 1

Medium 6.4

CVE-2026-71338

Windows Failover Cluster Elevation of Privilege Vulnerability

Double free in Windows Failover Cluster allows an authorized attacker to elevate privileges locally.

Microsoft Windows Server 2019 Windows Server 2019 (Server Core installation) Windows 10 Version 1809 Windows

Sep 8, 2026

Revision history

2026-09-08 #1
Information published.

References

CVE-2026-71338 Windows Failover Cluster Elevation of Privilege Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-71338
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