Type Confusion in Microsoft Windows and Windows Server - CVE-2026-34344

Vulnerability identifier: #VU131220

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-2026-34344

CWE-ID: CWE-843

Exploitation vector: Local access

Exploit availability: Public exploit is available

The vulnerability allows a local user to escalate privileges on the target system.

The vulnerability exists due to a type confusion error in Windows Ancillary Function Driver for WinSock. A local user can pass specially crafted data to the application, trigger a type confusion error and gain elevated privileges on the system.

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

• Exploit #13101 - CVE-2026-34344 (October 2, 2026)

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-34344

• Multiple vulnerabilities in Microsoft Windows Ancillary Function Driver for WinSock