HarborGuard / CVE
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HIGHCVE-2026-21251Published Modified CNA microsoft

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.

Metrics

CVSS v3.1
7.8
Severity
HIGH
Fixed in
10.0.14393.8868
Affected Products
8

Fix available

10.0.14393.886810.0.17763.838910.0.20348.477310.0.25398.214910.0.26100.32370
Patch commits
Affected packages
  • Microsoft / Windows Server 2016
    < 10.0.14393.8868 (from 10.0.14393.0)
  • Microsoft / Windows Server 2016 (Server Core installation)
    < 10.0.14393.8868 (from 10.0.14393.0)
  • Microsoft / Windows Server 2019
    < 10.0.17763.8389 (from 10.0.17763.0)
  • Microsoft / Windows Server 2019 (Server Core installation)
    < 10.0.17763.8389 (from 10.0.17763.0)
  • Microsoft / Windows Server 2022
    < 10.0.20348.4773 (from 10.0.20348.0)
  • Microsoft / Windows Server 2022, 23H2 Edition (Server Core installation)
    < 10.0.25398.2149 (from 10.0.25398.0)
  • Microsoft / Windows Server 2025
    < 10.0.26100.32370 (from 10.0.26100.0)
  • Microsoft / Windows Server 2025 (Server Core installation)
    < 10.0.26100.32370 (from 10.0.26100.0)
CVSS Vector
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
References