Protection Mechanism Failure in Microsoft products - CVE-2026-21513

Vulnerability identifier: #VU122547

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-2026-21513

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 compromise the affected system.

The vulnerability exists due to insufficient implementation of security measures within the ieframe.dll component when handling hyperlinks. An attacker can trick the the victim into clicking on a specially crafted link or on a shortcut (.lnk) file and execute arbitrary code on the system.

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

Microsoft Windows
Windows Server
Microsoft Internet Explorer

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-2026-21513
• https://cert.gov.ua/article/6287250
• https://www.akamai.com/blog/security-research/inside-the-fix-cve-2026-21513-mshtml-exploit-analysis

• Remote code execution in Microsoft MSHTML Framework