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Home - AdvisoriesPrint
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CERT-In Advisory CIAD-2021-0031

Remote Code Execution Vulnerability in Microsoft Windows MSHTML

Original Issue Date: September 09, 2021
Updated: September 15, 2021

Severity Rating: High

Software Affected

  • Windows 7 for 32-bit Systems Service Pack 1 and  x64-based Systems Service Pack 1
  • Windows 8.1 for 32-bit systems and  x64-based systems
  • Windows RT 8.1
  • Windows 10  for 32-bit Systems and  x64-based Systems
  • Windows 10 Version 1909 for 32-bit Systems,x64-based Systems, and ARM64-based Systems
  • Windows 10 Version 1809 for 32-bit Systems, x64-based Systems, and ARM64-based Systems
  • Windows 10 Version 20H2 for 32-bit Systems,x64-based Systems, and ARM64-based Systems
  • Windows 10 Version 21H1 for 32-bit Systems,x64-based Systems, and ARM64-based Systems
  • Windows 10 Version 1607 for 32-bit Systems and for x64-based Systems
  • Windows 10 Version 2004 for 32-bit Systems,x64-based Systems, and ARM64-based Systems
  • Windows Server, version 2004 (Server Core installation)
  • Windows Server, version 20H2 (Server Core Installation)
  • Windows Server 2008 R2 for x64-based Systems Service Pack 1 and Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation)
  • Windows Server 2008 for x64-based Systems Service Pack 2 and Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation)
  • Windows Server 2008 for 32-bit Systems Service Pack 2 and Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation)
  • Windows Server 2012 R2 and Windows Server 2012 R2 (Server Core installation)
  • Windows Server 2012 and Windows Server 2012 (Server Core installation)
  • Windows Server 2016 and Windows Server 2016 (Server Core installation)
  • Windows Server 2019 and Windows Server 2019 (Server Core installation)
  • Windows Server 2022 and Windows Server 2022 (Server Core installation)

Overview

A Vulnerability has been reported in Microsoft Windows MSHTML which could allow a remote attacker to execute arbitrary code on a targeted system.

Description

This vulnerability exists in Microsoft Windows MSHTML component due to improper validation of user supplied input. A remote, unauthenticated attacker could exploit this vulnerability by convincing a victim to open a specially crafted Microsoft office documents.

Successful exploitation of this vulnerability could allow a remote attacker to execute arbitrary code on the targeted system.

Note: This vulnerability is being actively exploited in the wild.

Solution

Apply appropriate updates as mentioned in Microsoft Security Guidance:  
https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-40444

Workaround

The workarounds listed below should be implemented after proper assessment.

Disable ActiveX controls on an individual system:

  • To disable installing ActiveX controls in Internet Explorer in all zones, paste the following into a text file and save it with the .reg file extension:
    Windows Registry Editor Version 5.00
    • [HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\0]
      "1001"=dword:00000003
      "1004"=dword:00000003
    • [HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\1]
      "1001"=dword:00000003
      "1004"=dword:00000003
    • HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\2]
      "1001"=dword:00000003
      "1004"=dword:00000003
    • HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3]
      "1001"=dword:00000003
      "1004"=dword:00000003
  • Double-click the .reg file to apply it to your Policy hive.
  • Reboot the system to ensure the new configuration is applied.

Vendor Information

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

References

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

CVE Name
CVE-2021-40444

Disclaimer

The information provided herein is on "as is" basis, without warranty of any kind.

Contact Information

Email: info@cert-in.org.in
Phone: +91-11-24368572

Postal address

Indian Computer Emergency Response Team (CERT-In)
Ministry of Electronics and Information Technology
Government of India
Electronics Niketan
6, CGO Complex, Lodhi Road,
New Delhi - 110 003
India

 
Indian Computer Emergency Response Team - CERT-In, Ministry of Electronics and Information Technology, Government of India.
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