Heap-based buffer overflow in Microsoft Windows and Windows Server - CVE-2025-26634

Vulnerability identifier: #VU107993

CSH Severity: Medium

CVSS v4: 7.7 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2025-26634

CWE-ID: CWE-122

Exploitation vector: Remote access

Exploit availability: No public exploit available

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

The vulnerability exists due to a boundary error in Windows Core Messaging. A remote user can send a specially crafted request to the system, trigger a heap-based buffer overflow and execute arbitrary code with SYSTEM privileges.

Microsoft Windows
Windows Server

Install updates from vendor's website.

Microsoft Windows - addressed in versions 10 21H2 10.0.19044.5487, 10 22H2 10.0.19045.5487, 10 1507 10.0.10240.20915, 10 1607 10.0.14393.7785, 10 1607 10.0.14393.7969, 10 1809 10.0.17763.6893, 11 22H2 10.0.22621.4890, 11 23H2 10.0.22631.4890, 11 24H2 10.0.26100.3194
Windows Server - addressed in versions 2008 R2 6.1.7601.27663, 2016 10.0.14393.7785, 2019 10.0.17763.6893, 2022 23H2 10.0.25398.1425, 2022 10.0.20348.3207, 2025 10.0.26100.3194

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-26634

• Privilege escalation in Microsoft Windows Core Messaging