Double free in Microsoft Windows and Windows Server - CVE-2026-20863
Published: January 13, 2026
Vulnerability identifier: #VU121237
CSH Severity: Low
CVSS v4: 7.3 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-20863
CWE-ID: CWE-415
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to escalate privileges on the system.
The vulnerability exists due to a boundary error in Win32k. A local user can pass specially crafted data to the application, trigger double free error and gain elevated privileges on the target system.
Affected software
Microsoft Windows
Windows Server
Windows Server
How to mitigate CVE-2026-20863
Install updates from vendor's website.
Microsoft Windows - addressed in versions 11 23H2 10.0.22631.6491, 11 24H2 10.0.26100.3223, 11 24H2 10.0.26100.7623
Windows Server - addressed in versions 2022 23H2 10.0.25398.2092, 2022 10.0.20348.4648, 2025 10.0.26100.7623, 2025 10.0.26100.32230
Windows Server - addressed in versions 2022 23H2 10.0.25398.2092, 2022 10.0.20348.4648, 2025 10.0.26100.7623, 2025 10.0.26100.32230