Vulnerability Monitor

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CVE-2021-40444

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 action to help protect our customers. This may include providing a security update through our monthly release process or providing an out-of-cycle security update, depending on customer needs. Please see the Mitigations and Workaround sections for important information about steps you can take to protect your system from this vulnerability. UPDATE September 14, 2021: Microsoft has released security updates to address this vulnerability. Please see the Security Updates table for the applicable update for your system. We recommend that you install these updates immediately. Please see the FAQ for important information about which updates are applicable to your system.

Security Impact Summary

This vulnerability carries a HIGH severity rating with a CVSS v3.1 score of 8.8, indicating it can be exploited remotely over the network with relatively low complexity though user interaction is required and does not require pre-existing privileges . The vulnerability impacts limited data confidentiality, integrity (unauthorized modifications), and limited availability for affected systems. Impacting 17 products from microsoft, from microsoft, from microsoft and 14 others, organizations running these solutions should prioritize assessment and patching.

Historical Context

Reported in 2021, this vulnerability emerged during an era marked by increased sophistication in supply chain attacks, cloud infrastructure vulnerabilities, and software-as-a-service (SaaS) security challenges. Security practices during this period emphasized zero-trust architectures, container security, and API protection.

Published

2021-09-15T12:15:16.467

Last Modified

2025-10-30T19:16:25.180

Status

Analyzed

Source

[email protected]

Severity

CVSSv3.1: 8.8 (HIGH)

CVSSv2 Vector

AV:N/AC:M/Au:N/C:P/I:P/A:P

Access Vector: NETWORK
Access Complexity: MEDIUM
Authentication: NONE
Confidentiality Impact: PARTIAL
Integrity Impact: PARTIAL
Availability Impact: PARTIAL

Exploitability Score

8.6

Impact Score

6.4

Weaknesses

Type: Primary
CWE-22
Type: Secondary
CWE-22

Affected Vendors & Products

Type	Vendor	Product	Version/Range	Vulnerable?
Operating System	microsoft	windows_10_1507	< 10.0.10240.19060	Yes
Operating System	microsoft	windows_10_1607	< 10.0.14393.4651	Yes
Operating System	microsoft	windows_10_1809	< 10.0.17763.2183	Yes
Operating System	microsoft	windows_10_1909	< 10.0.18363.1801	Yes
Operating System	microsoft	windows_10_2004	< 10.0.19041.1237	Yes
Operating System	microsoft	windows_10_20h2	< 10.0.19042.1237	Yes
Operating System	microsoft	windows_10_21h1	< 10.0.19043.1237	Yes
Operating System	microsoft	windows_7	-	Yes
Operating System	microsoft	windows_8.1	-	Yes
Operating System	microsoft	windows_rt_8.1	-	Yes
Operating System	microsoft	windows_server_2004	< 10.0.19041.1237	Yes
Operating System	microsoft	windows_server_2008	-	Yes
Operating System	microsoft	windows_server_2008	r2	Yes
Operating System	microsoft	windows_server_2012	-	Yes
Operating System	microsoft	windows_server_2012	-	Yes
Operating System	microsoft	windows_server_2016	< 10.0.14393.4651	Yes
Operating System	microsoft	windows_server_2019	< 10.0.17763.2183	Yes
Operating System	microsoft	windows_server_2022	< 10.0.20348.230	Yes
Operating System	microsoft	windows_server_20h2	< 10.0.19042.1237	Yes

References

http://packetstormsecurity.com/files/164210/Microsoft-Windows-MSHTML-Overview.html Third Party Advisory, VDB Entry ([email protected])
http://packetstormsecurity.com/files/165214/Microsoft-Office-Word-MSHTML-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry ([email protected])
http://packetstormsecurity.com/files/167317/Microsoft-Office-MSDT-Follina-Proof-Of-Concept.html Exploit, Third Party Advisory, VDB Entry ([email protected])
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40444 Mitigation, Patch, Vendor Advisory ([email protected])
http://packetstormsecurity.com/files/164210/Microsoft-Windows-MSHTML-Overview.html Third Party Advisory, VDB Entry (af854a3a-2127-422b-91ae-364da2661108)
http://packetstormsecurity.com/files/165214/Microsoft-Office-Word-MSHTML-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry (af854a3a-2127-422b-91ae-364da2661108)
http://packetstormsecurity.com/files/167317/Microsoft-Office-MSDT-Follina-Proof-Of-Concept.html Exploit, Third Party Advisory, VDB Entry (af854a3a-2127-422b-91ae-364da2661108)
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40444 Mitigation, Patch, Vendor Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40444 US Government Resource (134c704f-9b21-4f2e-91b3-4a467353bcc0)

How SecUtils Interprets This CVE

SecUtils normalizes and enriches National Vulnerability Database (NVD) records by standardizing vendor and product identifiers, aggregating vulnerability metadata from both NVD and MITRE sources, and providing structured context for security teams. For microsoft's affected products, we extract Common Platform Enumeration (CPE) data, Common Weakness Enumeration (CWE) classifications, CVSS severity metrics, and reference data to enable rapid vulnerability prioritization and asset correlation. This record contains no exploit code, proof-of-concept instructions, or attack methodologies—only defensive intelligence necessary for patch management, risk assessment, and security operations.