Heap-based buffer overflow in Microsoft Windows and Windows Server - CVE-2026-62739

Vulnerability identifier: #VU141540

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-2026-62739

CWE-ID: CWE-122

Exploitation vector: Local access

Exploit availability: No public exploit available

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

The vulnerability exists due to a boundary error in Windows HTTP.sys. A local user can pass specially crafted data to the application, trigger a heap-based buffer overflow and gain elevated privileges on the system.

Microsoft Windows
Windows Server

Install updates from vendor's website.

Microsoft Windows - addressed in versions 10 21H2 10.0.19044.7663, 10 22H2 10.0.19045.7663, 10 1809 10.0.17763.9115, 11 23H2 10.0.22631.7517, 11 24H2 10.0.26100.9106, 11 24H2 10.0.26100.9168, 11 25H2 10.0.26200.9168, 11 26H1 10.0.28000.2704
Windows Server - addressed in versions 2019 10.0.17763.9115, 2022 10.0.20348.5440, 2022 10.0.20348.5499, 2025 10.0.26100.33222, 2025 10.0.26100.33296

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62739

• Multiple vulnerabilities in Microsoft Windows HTTP.sys