CVE tracker / CVE-2026-71338
CVE-2026-71338
CVE-2026-71338 is the Windows Failover Cluster Elevation of Privilege Vulnerability. Microsoft rates it Important, CVSS 6.4. It is not in CISA's Known Exploited Vulnerabilities catalog. Published September 8, 2026.
Risk summary
MediumElevation of Privilege
6.4
CVSS v3 base
0.3%
EPSS: chance of exploitation in 30 days
Medium
Severity
Important
Microsoft's rating
Less Likely
Microsoft: exploitation
No
In CISA KEV
Microsoft describes it: “Double free in Windows Failover Cluster allows an authorized attacker to elevate privileges locally.”
How to fix it
Microsoft lists 16 affected products and the update that fixes each:
- KB5122871 · fixed build 10.0.26100.33438
Windows Server 2025, Windows Server 2025 (Server Core installation) - KB5122876 · fixed build 10.0.17763.9245
Windows Server 2019 (Server Core installation), Windows Server 2019, Windows 10 Version 1809 for 32-bit Systems, Windows 10 Version 1809 for x64-based Systems - KB5122882 · fixed build 10.0.20348.5622
Windows Server 2022 (Server Core installation), Windows Server 2022 - KB5123065 · fixed build 6.2.9200.26349
Windows Server 2012 (Server Core installation), Windows Server 2012 - KB5123066 · fixed build 6.3.9600.23398
Windows Server 2012 R2 (Server Core installation), Windows Server 2012 R2 - KB5123099 · fixed build 10.0.14393.9512
Windows Server 2016 (Server Core installation), Windows 10 Version 1607 for x64-based Systems, Windows Server 2016, Windows 10 Version 1607 for 32-bit Systems
What Microsoft changed
- September 8, 2026: Information published.
Details
- Weakness
- CWE-415: Double Free
- Publicly disclosed (Microsoft)
- No
- Exploited (Microsoft)
- No
- Known exploited (CISA KEV)
- Not listed
- Published
- September 8, 2026
- Last revised
- September 8, 2026
Get told when this changes
Senserva Watch emails Microsoft security and patch alerts when something moves: a new exploitation report, a revised fix, a known issue. Free, one email address.
References
From Microsoft, CISA, NVD and FIRST data; the Microsoft details were read when this page was opened. Check the references above before you act.