CVE-2021-40444

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.

Weakness: CWE-22.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

Required

Scope

Changed

Confidentiality impact

Low

Integrity impact

High

Availability impact

Low

Apply updates per vendor instructions.

Windows 10 Version 1507, Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 1909, Windows 10 Version 2004, Windows 10 Version 20H2, Windows 10 Version 21H1, Windows 7, Windows 7 Service Pack 1, Windows 8.1, Windows Server 2008 R2 Service Pack 1, Windows Server 2008 R2 Service Pack 1 (Server Core installation). NVD's record lists the exact affected versions.

• msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40444 PatchVendor Advisory
• portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40444 MitigationPatchVendor Advisory
• www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40444 US Government Resource