Use-after-free in Windows Server - CVE-2026-21251
Published: February 10, 2026
Vulnerability identifier: #VU122549
CSH Severity: Low
CVSS v4: 8.5 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-21251
CWE-ID: CWE-416
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to compromise vulnerable system.
The vulnerability exists due to a use-after-free error in Cluster Client Failover (CCF). A local user can gain elevated privileges on the target system.
Affected software
Windows Server
How to mitigate CVE-2026-21251
Install updates from vendor's website.
Windows Server - addressed in versions 2012 R2 6.3.9600.23022, 2016 10.0.14393.8868, 2019 10.0.17763.8389, 2022 23H2 10.0.25398.2149, 2022 10.0.20348.4711, 2022 10.0.20348.4773, 2025 10.0.26100.32313, 2025 10.0.26100.32370