Double free in Windows Server and Windows - CVE-2026-20863
Published: January 13, 2026
Vulnerability identifier: #VU121237
CSH Severity: Low
CVSS v4.0: 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/E:U/U:Clear
CVE-ID: CVE-2026-20863
CWE-ID: CWE-415
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vendor: Microsoft
Affected software:
Windows Server
Windows
Windows Server
Windows
Detailed vulnerability description
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.
How to mitigate CVE-2026-20863
Install updates from vendor's website.