NULL pointer dereference in Microsoft Windows and Windows Server - CVE-2026-40401

Vulnerability identifier: #VU131276

CSH Severity: Low

CVSS v4: 6.1 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:H]

CVE-ID: CVE-2026-40401

CWE-ID: CWE-476

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to a NULL pointer dereference error in Windows TCP/IP. A local attacker can pass specially crafted data to the application and perform a denial of service (DoS) attack.

Microsoft Windows
Windows Server

Install updates from vendor's website.

Microsoft Windows - addressed in versions 10 21H2 10.0.19044.7291, 10 22H2 10.0.19045.7291, 10 1607 10.0.14393.9140, 10 1809 10.0.17763.8755, 11 23H2 10.0.22631.7079, 11 24H2 10.0.26100.8390, 11 24H2 10.0.26100.8457, 11 25H2 10.0.26200.8390, 11 25H2 10.0.26200.8457, 11 26H1 10.0.28000.2113
Windows Server - addressed in versions 2012 R2 6.3.9600.23181, 2012 6.2.9200.26079, 2016 10.0.14393.9140, 2019 10.0.17763.8755, 2022 23H2 10.0.25398.2330, 2022 10.0.20348.5074, 2022 10.0.20348.5139, 2025 10.0.26100.32772, 2025 10.0.26100.32860

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40401

• Multiple vulnerabilities in Microsoft Windows TCP/IP