Protection Mechanism Failure in Microsoft Windows and Windows Server - CVE-2026-21510

Vulnerability identifier: #VU122544

CSH Severity: Critical

CVSS v4: 8.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-21510

CWE-ID: CWE-693

Exploitation vector: Remote access

Exploit availability: The vulnerability is being exploited in the wild

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

The vulnerability exists due to insufficient implementation of security measures. An attacker can trick the victim into clicking on a specially crafted URL or shortcut file to bypass Windows SmartScreen and Windows Shell security prompts and execute arbitrary code on the system.

Note, the vulnerability is being actively exploited in the wild.

Microsoft Windows
Windows Server

Install updates from vendor's website.

Microsoft Windows - addressed in versions 10 21H2 10.0.19044.6937, 10 22H2 10.0.19045.6937, 10 1607 10.0.14393.8868, 10 1809 10.0.17763.8389, 11 23H2 10.0.22631.6649, 11 24H2 10.0.26100.7781, 11 24H2 10.0.26100.7840, 11 26H1 10.0.28000.1575
Windows Server - addressed in versions 2012 R2 6.3.9600.23022, 2012 6.2.9200.25923, 2016 10.0.14393.8868, 2019 10.0.17763.8389, 2022 23H2 10.0.25398.2149, 2022 10.0.20348.4711, 2022 10.0.20348.4773, 2025 10.0.26100.32313, 2025 10.0.26100.32370

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21510

• Security feature bypass vulnerability in Windows Shell