CVE-2026-21251
Cluster Client Failover (CCF) Elevation of Privilege Vulnerability
Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Cluster Client Failover (CCF) Elevation of Privilege Vulnerability
Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.
- Record
CVE-2026-21251- CVSS 3.1
- 7.8 High
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 - Weakness
- CWE-416
- Updated
- 2026-11-02
EUVDEUVD-2026-7326
Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.
- Record
EUVD-2026-7326- CVSS 3.1
- 7.8 High
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 - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-6q2h-rrfg-fm75
Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate...
Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.
- Record
GHSA-6q2h-rrfg-fm75- CVSS 3.1
- 7.8 High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-416
- Updated
- 2026-11-02
NVD
Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.
- Record
CVE-2026-21251- CVSS 3.1
- 7.8 High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-416
- Updated
- 2026-11-02
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)
- microsoft windows server 2022 23h2
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-21251 is a high vulnerability (CVSS 7.8) in Microsoft Windows Server 2016, published February 10, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.44%, the 38th percentile. No source names a fixed version.