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CVE-2021-40444
HIGH · CVSS 8.8 ⚠ KEV — EXPLOITED
EPSS exploitation probability: 100%
⚠ Listed in the CISA Known Exploited Vulnerabilities catalog — actively exploited.
Published 2021-11-03 · Last modified 2026-08-10T16:18:12.920

Summary

Microsoft is investigating reports of a remote code execution vulnerability in MSHTML that affects Microsoft Windows. Microsoft is aware of targeted attacks that attempt to exploit this vulnerability by using specially-crafted Microsoft Office documents. An attacker could craft a malicious ActiveX control to be used by a Microsoft Office document that hosts the browser rendering engine. The attacker would then have to convince the user to open the malicious document. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. Microsoft Defender Antivirus and Microsoft Defender for Endpoint both provide detection and protections for the known vulnerability. Customers should keep antimalware produc

Affected products

Microsoft — MSHTML

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References

This product uses data from the NVD API but is not endorsed or certified by the NVD. Informational only; not professional security advice.