Known Exploited Vulnerability
8.8
HIGH CVSS 3.1
CVE-2021-40444
Microsoft MSHTML Remote Code Execution Vulnerability - [Actively Exploited]
Description

<p>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.</p> <p>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.</p> <p>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”.</p> <p>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.</p> <p>Please see the <strong>Mitigations</strong> and <strong>Workaround</strong> sections for important information about steps you can take to protect your system from this vulnerability.</p> <p><strong>UPDATE</strong> 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.</p>

INFO

Published Date :

Sept. 15, 2021, 12:15 p.m.

Last Modified :

April 4, 2025, 8:46 p.m.

Remotely Exploit :

Yes !
CISA Notification
CISA KEV (Known Exploited Vulnerabilities)

For the benefit of the cybersecurity community and network defenders—and to help every organization better manage vulnerabilities and keep pace with threat activity—CISA maintains the authoritative source of vulnerabilities that have been exploited in the wild.

Description :

Microsoft MSHTML contains a unspecified vulnerability that allows for remote code execution.

Required Action :

Apply updates per vendor instructions.

Notes :

https://nvd.nist.gov/vuln/detail/CVE-2021-40444

Affected Products

The following products are affected by CVE-2021-40444 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Microsoft windows_10
2 Microsoft windows_7
3 Microsoft windows_8.1
4 Microsoft windows_rt_8.1
5 Microsoft windows_server_2008
6 Microsoft windows_server_2012
7 Microsoft windows_server_2016
8 Microsoft windows_server_2019
9 Microsoft windows_10_1607
10 Microsoft windows_10_1809
11 Microsoft windows_10_20h2
12 Microsoft windows_server_2022
13 Microsoft windows_10_1507
14 Microsoft windows_10_21h1
15 Microsoft windows_10_1909
16 Microsoft windows_server_20h2
17 Microsoft windows_10_2004
18 Microsoft windows_server_2004
19 Microsoft windows_server_2012_r2
20 Microsoft windows_server_2008_r2
21 Microsoft windows_server_2008_sp2
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.
Score Version Severity Vector Exploitability Score Impact Score Source
CVSS 2.0 MEDIUM [email protected]
CVSS 3.1 HIGH [email protected]
CVSS 3.1 HIGH [email protected]
Solution
This addresses a remote code execution vulnerability in Microsoft Windows MSHTML.
  • Apply the latest available security updates for Windows.
  • If updates are unavailable, use Microsoft's mitigation steps.
Public PoC/Exploit Available at Github

CVE-2021-40444 has a 132 public PoC/Exploit available at Github. Go to the Public Exploits tab to see the list.

References to Advisories, Solutions, and Tools
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2021-40444 is associated with the following CWEs:

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

None

Updated: 1 week, 1 day ago
0 stars 0 fork 0 watcher
Born at : Aug. 15, 2025, 9:07 a.m. This repo has been linked 310 different CVEs too.

None

Updated: 1 week, 3 days ago
0 stars 0 fork 0 watcher
Born at : Aug. 7, 2025, 10:50 a.m. This repo has been linked 1 different CVEs too.

Vulnerabilidades Conhecidas em Sistemas Windows Desatualizados

Updated: 1 month, 1 week ago
0 stars 0 fork 0 watcher
Born at : July 13, 2025, 3:24 p.m. This repo has been linked 17 different CVEs too.

Macros, Malware, and mayhem: Your cyber kill chain training grounds.

Updated: 3 months, 2 weeks ago
0 stars 0 fork 0 watcher
Born at : May 5, 2025, 2:16 a.m. This repo has been linked 1 different CVEs too.

In the evolving landscape of cybersecurity, it's essential that defenders are equipped not only with knowledge of threats but also with hands-on skills in dissecting them.

Updated: 4 months, 1 week ago
0 stars 0 fork 0 watcher
Born at : April 13, 2025, 6:40 a.m. This repo has been linked 1 different CVEs too.

None

Updated: 4 days, 16 hours ago
4 stars 0 fork 0 watcher
Born at : April 8, 2025, 1:23 p.m. This repo has been linked 11 different CVEs too.

Full phishing campaign simulation using GoPhish, OSINT, spoofed domains, and HTML harvesters for red team ops.

Updated: 3 weeks, 3 days ago
0 stars 0 fork 0 watcher
Born at : April 2, 2025, 9:51 a.m. This repo has been linked 1 different CVEs too.

This is my starred repositories including the description for each tool. Makes search/filter over them easier.

Updated: 1 month ago
51 stars 6 fork 6 watcher
Born at : Feb. 26, 2025, 11:57 a.m. This repo has been linked 91 different CVEs too.

None

HTML Python Shell

Updated: 1 month, 2 weeks ago
0 stars 0 fork 0 watcher
Born at : Feb. 13, 2025, 8:50 a.m. This repo has been linked 891 different CVEs too.

This is my personal collection of malware development notes, tools, code snippets, and resources I explore and learn from. It’s my go-to place to keep everything organized and handy.

Updated: 6 days, 19 hours ago
0 stars 0 fork 0 watcher
Born at : Dec. 25, 2024, 4:48 p.m. This repo has been linked 12 different CVEs too.

None

Batchfile VBA Python HTML

Updated: 9 months ago
0 stars 0 fork 0 watcher
Born at : Nov. 21, 2024, 5:27 a.m. This repo has been linked 1 different CVEs too.

Blogs/CVEs/Talks/Patents

Updated: 8 months ago
0 stars 0 fork 0 watcher
Born at : Oct. 2, 2024, 7:23 p.m. This repo has been linked 4 different CVEs too.

None

Batchfile VBA Python HTML

Updated: 11 months ago
0 stars 0 fork 0 watcher
Born at : Sept. 23, 2024, 8:52 a.m. This repo has been linked 1 different CVEs too.

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.

Python Batchfile HTML JavaScript PowerShell VBScript

Updated: 1 year ago
0 stars 0 fork 0 watcher
Born at : July 28, 2024, 5:23 p.m. This repo has been linked 1 different CVEs too.

For learning purpose did a complete analysis on CVE-2021-40444 POC (proof of concept)

Rust HTML

Updated: 1 year, 1 month ago
0 stars 1 fork 1 watcher
Born at : June 14, 2024, 7:04 p.m. This repo has been linked 1 different CVEs too.

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2021-40444 vulnerability anywhere in the article.

  • Kaspersky
Exploits and vulnerabilities in Q3 2024

Q3 2024 saw multiple vulnerabilities discovered in Windows and Linux subsystems that are not standard for cyberattacks. This is because operating system developers have been releasing new security mit ... Read more

Published Date: Dec 06, 2024 (8 months, 2 weeks ago)
  • Kaspersky
Exploits and vulnerabilities in Q2 2024

Q2 2024 was eventful in terms of new interesting vulnerabilities and exploitation techniques for applications and operating systems. Attacks through vulnerable drivers have become prevalent as a gener ... Read more

Published Date: Aug 21, 2024 (1 year ago)
  • Trend Micro
CVE-2024-38112: Void Banshee Targets Windows Users Through Zombie Internet Explorer in Zero-Day Attacks

Exploits & Vulnerabilities Our threat hunters discovered CVE-2024-38112, which was used as a zero-day by APT group Void Banshee, to access and execute files through the disabled Internet Explorer usin ... Read more

Published Date: Jul 15, 2024 (1 year, 1 month ago)
  • huntress.com
Rapid Response: Microsoft Office RCE - “Follina” MSDT Attack | Huntress

This post, as is the norm for emerging threats, is a developing article and may be subject to change as the Huntress team learns more about this attack vector and new information is available.UPDATE 4 ... Read more

Published Date: May 30, 2022 (3 years, 2 months ago)
  • huntress.com
Threat Advisory: Hackers Are Exploiting CVE-2021-40444 | Huntress

On September 7, Huntress was made aware of a new threat against Windows operating systems and Microsoft Office products. With the identifier CVE-2021-40444, the MSHTML engine is vulnerable to arbitrar ... Read more

Published Date: Sep 09, 2021 (3 years, 11 months ago)

The following table lists the changes that have been made to the CVE-2021-40444 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • Modified Analysis by [email protected]

    Apr. 04, 2025

    Action Type Old Value New Value
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Feb. 04, 2025

    Action Type Old Value New Value
    Added CWE CWE-22
  • CVE Modified by af854a3a-2127-422b-91ae-364da2661108

    Nov. 21, 2024

    Action Type Old Value New Value
    Added Reference http://packetstormsecurity.com/files/164210/Microsoft-Windows-MSHTML-Overview.html
    Added Reference http://packetstormsecurity.com/files/165214/Microsoft-Office-Word-MSHTML-Remote-Code-Execution.html
    Added Reference http://packetstormsecurity.com/files/167317/Microsoft-Office-MSDT-Follina-Proof-Of-Concept.html
    Added Reference https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40444
  • Modified Analysis by [email protected]

    Jul. 29, 2024

    Action Type Old Value New Value
    Changed Reference Type http://packetstormsecurity.com/files/164210/Microsoft-Windows-MSHTML-Overview.html Exploit, Third Party Advisory, VDB Entry http://packetstormsecurity.com/files/164210/Microsoft-Windows-MSHTML-Overview.html Third Party Advisory, VDB Entry
    Changed CPE Configuration OR *cpe:2.3:o:microsoft:windows_10:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:20h2:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:21h1:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:1607:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:1809:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:1909:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:2004:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_7:-:sp1:*:*:-:*:-:* *cpe:2.3:o:microsoft:windows_8.1:-:*:*:*:-:*:-:* *cpe:2.3:o:microsoft:windows_rt_8.1:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:x64:* *cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2012:-:r2:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2016:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2016:20h2:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2016:2004:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2019:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2022:-:*:*:*:*:*:*:* OR *cpe:2.3:o:microsoft:windows_10_1507:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.10240.19060 *cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.14393.4651 *cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.17763.2183 *cpe:2.3:o:microsoft:windows_10_1909:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.18363.1801 *cpe:2.3:o:microsoft:windows_10_2004:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.19041.1237 *cpe:2.3:o:microsoft:windows_10_20h2:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.19042.1237 *cpe:2.3:o:microsoft:windows_10_21h1:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.19043.1237 *cpe:2.3:o:microsoft:windows_7:-:sp1:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_8.1:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_rt_8.1:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2004:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.19041.1237 *cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:x64:* *cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2012:-:r2:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.14393.4651 *cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.17763.2183 *cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.20348.230 *cpe:2.3:o:microsoft:windows_server_20h2:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.19042.1237
  • CVE Modified by [email protected]

    May. 14, 2024

    Action Type Old Value New Value
  • CVE Modified by [email protected]

    Dec. 28, 2023

    Action Type Old Value New Value
    Changed Description Microsoft MSHTML Remote Code Execution Vulnerability <p>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.</p> <p>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.</p> <p>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”.</p> <p>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.</p> <p>Please see the <strong>Mitigations</strong> and <strong>Workaround</strong> sections for important information about steps you can take to protect your system from this vulnerability.</p> <p><strong>UPDATE</strong> 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.</p>
    Added CVSS V3.1 Microsoft Corporation AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L
  • Modified Analysis by [email protected]

    Oct. 14, 2022

    Action Type Old Value New Value
    Changed Reference Type http://packetstormsecurity.com/files/167317/Microsoft-Office-MSDT-Follina-Proof-Of-Concept.html No Types Assigned http://packetstormsecurity.com/files/167317/Microsoft-Office-MSDT-Follina-Proof-Of-Concept.html Exploit, Third Party Advisory, VDB Entry
  • CWE Remap by [email protected]

    Jul. 12, 2022

    Action Type Old Value New Value
    Changed CWE NVD-CWE-noinfo CWE-22
  • CVE Modified by [email protected]

    Jun. 02, 2022

    Action Type Old Value New Value
    Added Reference http://packetstormsecurity.com/files/167317/Microsoft-Office-MSDT-Follina-Proof-Of-Concept.html [No Types Assigned]
  • Modified Analysis by [email protected]

    Dec. 15, 2021

    Action Type Old Value New Value
    Changed Reference Type http://packetstormsecurity.com/files/164210/Microsoft-Windows-MSHTML-Overview.html Exploit, Third Party Advisory http://packetstormsecurity.com/files/164210/Microsoft-Windows-MSHTML-Overview.html Exploit, Third Party Advisory, VDB Entry
    Changed Reference Type http://packetstormsecurity.com/files/165214/Microsoft-Office-Word-MSHTML-Remote-Code-Execution.html No Types Assigned http://packetstormsecurity.com/files/165214/Microsoft-Office-Word-MSHTML-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry
  • CVE Modified by [email protected]

    Dec. 09, 2021

    Action Type Old Value New Value
    Added Reference http://packetstormsecurity.com/files/165214/Microsoft-Office-Word-MSHTML-Remote-Code-Execution.html [No Types Assigned]
  • Initial Analysis by [email protected]

    Sep. 24, 2021

    Action Type Old Value New Value
    Added CVSS V2 Metadata Victim must voluntarily interact with attack mechanism
    Added CVSS V2 NIST (AV:N/AC:M/Au:N/C:P/I:P/A:P)
    Added CVSS V3.1 NIST AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
    Changed Reference Type http://packetstormsecurity.com/files/164210/Microsoft-Windows-MSHTML-Overview.html No Types Assigned http://packetstormsecurity.com/files/164210/Microsoft-Windows-MSHTML-Overview.html Exploit, Third Party Advisory
    Changed Reference Type https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40444 No Types Assigned https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40444 Mitigation, Patch, Vendor Advisory
    Added CWE NIST NVD-CWE-noinfo
    Added CPE Configuration OR *cpe:2.3:o:microsoft:windows_10:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:20h2:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:21h1:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:1607:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:1809:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:1909:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:2004:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_7:-:sp1:*:*:-:*:-:* *cpe:2.3:o:microsoft:windows_8.1:-:*:*:*:-:*:-:* *cpe:2.3:o:microsoft:windows_rt_8.1:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:x64:* *cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2012:-:r2:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2016:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2016:20h2:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2016:2004:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2019:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2022:-:*:*:*:*:*:*:*
  • CVE Modified by [email protected]

    Sep. 20, 2021

    Action Type Old Value New Value
    Added Reference http://packetstormsecurity.com/files/164210/Microsoft-Windows-MSHTML-Overview.html [No Types Assigned]
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
Vulnerability Scoring Details
Base CVSS Score: 8.8
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality Impact
Integrity Impact
Availability Impact
Base CVSS Score: 6.8
Access Vector
Access Complexity
Authentication
Confidentiality Impact
Integrity Impact
Availability Impact
Exploit Prediction

EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days.

94.29 }} -0.06%

score

0.99931

percentile