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CVE-2021-40444

Microsoft MSHTML Remote Code Execution Vulnerability

Basic Information

CVE State: PUBLISHED
Reserved Date: September 02, 2021
Published Date: September 15, 2021
Last Updated: February 04, 2025
Vendor: Microsoft
Product: Windows 10 Version 1809, Windows Server 2019, Windows Server 2019 (Server Core installation), Windows 10 Version 1909, Windows 10 Version 21H1, Windows Server 2022, Windows 10 Version 2004, Windows Server version 2004, Windows 10 Version 20H2, Windows Server version 20H2, Windows 10 Version 1507, Windows 10 Version 1607, Windows Server 2016, Windows Server 2016 (Server Core installation), Windows 7, Windows 7 Service Pack 1, Windows 8.1, Windows Server 2008 Service Pack 2, Windows Server 2008 Service Pack 2 (Server Core installation), Windows Server 2008 Service Pack 2, Windows Server 2008 R2 Service Pack 1, Windows Server 2008 R2 Service Pack 1 (Server Core installation), Windows Server 2012, Windows Server 2012 (Server Core installation), Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation)
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 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.

CVSS Scores

CVSS v3.1

8.8 - HIGH

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L/E:P/RL:O/RC:C

SSVC Information

Exploitation: active
Technical Impact: total

Exploit Status

Exploited in the Wild: Yes (added 2021-11-03 00:00:00 UTC) Source
Proof of Concept Available: Yes (added 2023-06-05 02:27:21 UTC) Source
Used in Malware: Yes (added 2021-11-03 00:00:00 UTC) Source

References

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40444 http://packetstormsecurity.com/files/164210/Microsoft-Windows-MSHTML-Overview.html http://packetstormsecurity.com/files/165214/Microsoft-Office-Word-MSHTML-Remote-Code-Execution.html http://packetstormsecurity.com/files/167317/Microsoft-Office-MSDT-Follina-Proof-Of-Concept.html

Known Exploited Vulnerability Information

Source	Added Date
CISA	2021-11-03 00:00:00 UTC

Scanner Integrations

Scanner	URL	Date Detected
Metasploit	https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/windows/fileformat/word_mshtml_rce.rb	2025-04-29 11:01:36 UTC

Potential Proof of Concepts

Warning: These PoCs have not been tested and could contain malware. Use at your own risk.

word_mshtml_rce

Type: metasploit • Created: Unknown

Metasploit module for CVE-2021-40444

basim-ahmad/Follina-CVE-and-CVE-2021-40444

Type: github • Created: 2024-07-28 17:23:43 UTC • Stars: 0

This repository contains scripts and resources for exploiting the Follina CVE and CVE-2021-40444 vulnerabilities in Microsoft Office. The scripts generate malicious document files that can execute arbitrary code on the target system.