CVE-2026-21251 json
Cluster Client Failover (CCF) Elevation of Privilege Vulnerability
published 2026-02-10 8 mo ago modified 2026-08-19 2 mo ago also EUVD-2026-7326
- cvss
- 7.8
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 38%
- public exploits
- 0
- none known
Summary
Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.
Patch / fix
- Microsoft Windows Server 2016 10.0.14393.8868
- Microsoft Windows Server 2016 (Server Core installation) 10.0.14393.8868
- Microsoft Windows Server 2019 10.0.17763.8389
- Microsoft Windows Server 2019 (Server Core installation) 10.0.17763.8389
- Microsoft Windows Server 2022 10.0.20348.4773
- Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.2149
- Microsoft Windows Server 2025 10.0.26100.32370
- Microsoft Windows Server 2025 (Server Core installation) 10.0.26100.32370
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- 8 mo ago
Exploit prediction
0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C |
| CNA | 3.1 | 7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
Affected products
- Microsoft Windows Server 2016
- Microsoft Windows Server 2016 (Server Core installation)
- Microsoft Windows Server 2019
- Microsoft Windows Server 2019 (Server Core installation)
- Microsoft Windows Server 2022
- Microsoft Windows Server 2022, 23H2 Edition (Server Core installation)
- Microsoft Windows Server 2025
- Microsoft Windows Server 2025 (Server Core installation)
Classification
- Weakness
-
- CWE-416 Use After Free
References
-
msrc.microsoft.com
/update-guide/vulnerability/CVE-2026-21251
vendor-advisory, patch
Sources
- CVE List CVE-2026-21251
- NVD CVE-2026-21251
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