Attacker Value
Moderate
(4 users assessed)
Exploitability
Low
(4 users assessed)
User Interaction
Required
Privileges Required
None
Attack Vector
Local
9

CVE-2021-40444

Disclosure Date: September 15, 2021
Exploited in the Wild
Add MITRE ATT&CK tactics and techniques that apply to this CVE.
Execution
Techniques
Validation
Validated
Validated
Validated

Description

Microsoft MSHTML Remote Code Execution Vulnerability

Add Assessment

3
Ratings
Technical Analysis
  • Vulnerable if default behaviour has been changed ( By default, Microsoft Office opens documents from the internet in Protected View or Application Guard for Office both of which prevent the current attack )
  • Requires social engineering to be exploited
  • Workaround easy to deploy
2
Ratings
Technical Analysis

CVE-2021-40444

Vulnerability:

  • Microsoft MSHTML Remote Code Execution Vulnerability
  • Tested with malicious .exe file

Executive Summary:

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.


Conclusion:

  • Security is not checked
  • Just OPEN :D

Risk Assessment:

  • This may well be a meterpreter malicious backdoor shell file
  • This may well be a malicious MSI package or hidden bat file

Status:

  • Low(Medium)

Fixed

  • Windows 11

Source:

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Reproduce:

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Demo docx:

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Demo VLC:

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1
Ratings
Technical Analysis

Microsoft MSHTML Remote Code Execution Vulnerability
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.

A threat actor 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.

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40444

CVSS V3 Severity and Metrics
Base Score:
7.8 High
Impact Score:
5.9
Exploitability Score:
1.8
Vector:
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Attack Vector (AV):
Local
Attack Complexity (AC):
Low
Privileges Required (PR):
None
User Interaction (UI):
Required
Scope (S):
Unchanged
Confidentiality (C):
High
Integrity (I):
High
Availability (A):
High

General Information

Vendors

  • Microsoft

Products

  • Windows,
  • Windows Server,
  • Windows 10 Version 1909 for 32-bit Systems,
  • Windows 10 Version 1909 for x64-based Systems,
  • Windows 10 Version 1909 for ARM64-based Systems,
  • Windows 10 Version 21H1 for x64-based Systems,
  • Windows 10 Version 21H1 for ARM64-based Systems,
  • Windows 10 Version 21H1 for 32-bit Systems,
  • Windows Server 2022,
  • Windows Server 2022 (Server Core installation),
  • Windows 10 Version 2004 for 32-bit Systems,
  • Windows 10 Version 2004 for ARM64-based Systems,
  • Windows 10 Version 2004 for x64-based Systems,
  • Windows Server, version 2004 (Server Core installation),
  • Windows 10 Version 20H2 for x64-based Systems,
  • Windows 10 Version 20H2 for 32-bit Systems,
  • Windows 10 Version 20H2 for ARM64-based Systems,
  • Windows Server, version 20H2 (Server Core Installation)

Exploited in the Wild

Reported by:

Additional Info

Technical Analysis