Protection Mechanism Failure in Microsoft Windows and Windows Server - CVE-2025-21217

Vulnerability identifier: #VU102731

CSH Severity: Medium

CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2025-21217

CWE-ID: CWE-693

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to bypass implemented security restrictions.

The vulnerability exists due to insufficient implementation of security measures in Windows NTLM. A remote attacker can bypass implemented security restrictions and spoof page content.

Microsoft Windows
Windows Server

Install updates from vendor's website.

Microsoft Windows - addressed in versions 10 21H2 10.0.19044.5371, 10 22H2 10.0.19045.5371, 10 1507 10.0.10240.20890, 10 1607 10.0.14393.7699, 10 1809 10.0.17763.6775, 11 22H2 10.0.22621.4751, 11 23H2 10.0.22631.4751, 11 24H2 10.0.26100.3107
Windows Server - addressed in versions 2008 R2 6.1.7601.27520, 2008 6.0.6003.23070, 2012 R2 6.3.9600.22371, 2012 6.2.9200.25273, 2016 10.0.14393.7785, 2022 23H2 10.0.25398.1369, 2022 10.0.20348.3091, 2025 10.0.26100.2894

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2025-21217

• Protection Mechanism Failure in Microsoft Windows NTLM