Heap-based buffer overflow in Microsoft Windows and Windows Server - CVE-2026-119840

Vulnerability identifier: #VU165274

CSH Severity: Low

CVSS v4: 5.4 [CVSS:4.0/AV:P/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-119840

CWE-ID: CWE-122

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a user with physical access to system to escalate privileges to SYSTEM.

The vulnerability exists due to a heap-based buffer overflow in the Windows Universal Disk Format File System Driver (UDFS) when handling file system operations. A user with physical access to system can trigger memory corruption in the driver to gain SYSTEM privileges.

Microsoft Windows
Windows Server

Install security update from vendor's website.

Microsoft Windows - addressed in versions 10 21H2 10.0.19044.7846, 10 22H2 10.0.19045.7846, 10 1607 10.0.14393.9688, 10 1809 10.0.17763.9487, 11 23H2 10.0.22631.7711, 11 24H2 10.0.26100.9911, 11 24H2 10.0.26100.9974, 11 25H2 10.0.26200.9911, 11 25H2 10.0.26200.9974, 11 26H1 10.0.28000.3501
Windows Server - addressed in versions 2016 10.0.14393.9688, 2019 10.0.17763.9487, 2022 10.0.20348.5870, 2025 10.0.26100.33730, 2025 10.0.26100.33822

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-119840
• https://support.microsoft.com/help/5131291

• Multiple vulnerabilities in Microsoft Windows