Multiple Microsoft Office versions impacted by an actively exploited zero-day

A zero-day flaw in Microsoft Office that could be exploited by attackers to achieve arbitrary code execution on Windows systems.

The cybersecurity researcher nao_sec discovered a malicious Word document (“05-2022-0438.doc”) that was uploaded to VirusTotal from Belarus. The document uses the remote template feature to fetch an HTML and then uses the “ms-msdt” scheme to execute PowerShell code.

The popular cybersecurity expert Kevin Beaumont published an analysis of the flaw.

“The document uses the Word remote template feature to retrieve a HTML file from a remote webserver, which in turn uses the ms-msdt MSProtocol URI scheme to load some code and execute some PowerShell.” reads the analysis published by Beaumont. “There’s a lot going on here, but the first problem is Microsoft Word is executing the code via msdt (a support tool) even if macros are disabled. Protected View does kick in, although if you change the document to RTF form, it runs without even opening the document (via the preview tab in Explorer) let alone Protected View.”

The issue affects multiple Microsoft Office versions, including Office, Office 2016, and Office 2021.

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Pierluigi Paganini

(SecurityAffairs – hacking, domain name system)