Heap-based buffer overflow in Microsoft Windows and Windows Server - CVE-2026-21245
Published: February 10, 2026
Vulnerability identifier: #VU122539
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-2026-21245
CWE-ID: CWE-122
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 Windows Kernel. A local user can pass specially crafted data to the application, trigger a heap-based buffer overflow and gain elevated privileges on the target system.
Affected software
Microsoft Windows
Windows Server
Windows Server
How to mitigate CVE-2026-21245
Install updates from vendor's website.
Microsoft Windows - addressed in versions 11 24H2 10.0.26100.7781, 11 24H2 10.0.26100.7840, 11 26H1 10.0.28000.1575
Windows Server - addressed in versions 2012 R2 6.3.9600.23022, 2025 10.0.26100.32313, 2025 10.0.26100.32370
Windows Server - addressed in versions 2012 R2 6.3.9600.23022, 2025 10.0.26100.32313, 2025 10.0.26100.32370