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CVE-2021-40444

CWE-22

Critical

97.8

RPS

Description

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 products up to date. Customers who utilize automatic updates do not need to take additional action. Enterprise customers who manage updates should select the detection build 1.349.22.0 or newer and deploy it across their environments. Microsoft Defender for Endpoint alerts will be displayed as: “Suspicious Cpl File Execution”. Upon completion of this investigation, Microsoft will take the appropriate a…

Source: NVD

Signals

CVSS
8.8
High · v3.1
EPSS
97.45%
Probability of exploitation in the next 30 days (FIRST)
CISA KEV
In CISA KEV since Nov 2021
Fix commit
No known fix commit
Sources: MoreFixes, FreshFixes
Weakness
CWE-22
Published
15 Sept 2021
Last modified 10 Aug 2026

How to read these signals: RPS · EPSS · CISA KEV · Data sources

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Data as of 7 Oct 2026, 05:16 UK time

CVE-2021-40444 · RPS 97.8 · DevSecure Intelligence