CVE-2021-40444 is a high-severity vulnerability affecting Microsoft Windows operating systems, including various versions of Windows and Windows Server. This vulnerability, known as the Microsoft MSHTML Remote Code Execution Vulnerability, allows attackers to execute malicious code on a victim's computer through specially-crafted Microsoft Office documents. It is important for users to be aware of this vulnerability and take necessary precautions to protect their systems from potential attacks.

How do I know if I'm affected?

If you're concerned about this vulnerability, it's important to know that it affects various versions of Microsoft Windows, Microsoft Office, and Windows Server. This vulnerability allows an attacker to craft a malicious ActiveX control to be used by a Microsoft Office document that hosts the browser rendering engine. Microsoft Defender Antivirus and Microsoft Defender for Endpoint provide detection and protections for this vulnerability. To see if you're affected, check if you're using any of the mentioned affected versions of Windows, Office, or Windows Server.

What should I do if I'm affected?

If you're affected by this vulnerability, follow these simple steps to protect your system:

1. Keep your antimalware products up to date. Microsoft Defender Antivirus and Microsoft Defender for Endpoint provide detection and protection for this vulnerability.

2. Disable the installation of all ActiveX controls in Internet Explorer to prevent exploitation.

3. Monitor Microsoft's Security Update Guide for any updates or patches related to this vulnerability.

Is this in CISA’s Known Exploited Vulnerabilities Catalog?

This vulnerability, also known as the Microsoft MSHTML Remote Code Execution Vulnerability, is present in CISA's Known Exploited Vulnerabilities Catalog. It was added on 11/03/2021, and organizations are required to address it by 11/17/2021. The necessary action is to apply updates according to vendor instructions. This vulnerability allows attackers to execute malicious code remotely by using specially-crafted Microsoft Office documents.

Weakness enumeration

The weakness enumeration for this vulnerability is categorized as CWE-22. This vulnerability allows attackers to exploit specially-crafted Microsoft Office documents using malicious ActiveX controls, potentially leading to remote code execution.

For more details

The CVE-2021-40444 vulnerability poses a significant risk to organizations and individuals using Microsoft Office and MSHTML. Various sources have provided in-depth analysis, alternative exploitation paths, and proof-of-concept demonstrations. It is crucial to stay informed and apply necessary updates and mitigations to protect against this threat. For more information about this vulnerability, visit the NVD page or the links below.

• Microsoft Windows MSHTML Overview

• Microsoft Office Word MSHTML Remote Code Execution

• Microsoft Office MSDT Follina Proof Of Concept

• Microsoft MSHTML Remote Code Execution Vulnerability