Emergency Patch Issued for Microsoft Office, 365 Over Hacking Threat

Microsoft has released an emergency patch for a vulnerability in the company’s Office programs that’s already being exploited by hackers. 

On Monday, the company disclosed the flaw, CVE-2026-21509, which affects Microsoft 365 Apps for Enterprise and Microsoft Office 2019 and 2016, in addition to the Microsoft Office LTSC (Long-Term Service Channel) 2024 and Microsoft Office LTSC 2021.

Microsoft suggests the threat is being used in phishing attacks against vulnerable systems. That’s because successful exploitation requires local access to the PC, which could involve tricking the user into opening a malicious document.

“Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally,” adds a report from cybersecurity authority CVE.org. That feature is Object Linking and Embedding (OLE), which can integrate content, images, and links from different applications into one document. 

“This update addresses a vulnerability that bypasses OLE mitigations in Microsoft 365 and Microsoft Office which protect users from vulnerable COM/OLE controls,” the company said without elaborating. Microsoft also warns that hackers have already been abusing the bug, including circulating computer code to exploit the attack. 

The company’s patch is already rolling out. “Customers on Office 2021 and later will be automatically protected via a service-side change, but will be required to restart their Office applications for this to take effect,” the company says.

But in some bad news, Microsoft is still working to release a patch for Microsoft Office 2016 and 2019. Still, the company says customers on these versions can follow steps in its vulnerability report, including adding new registry keys to protect them from the threat. 

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Michael Kan

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I’ve been a journalist for over 15 years. I got my start as a schools and cities reporter in Kansas City and joined PCMag in 2017, where I cover satellite internet services, cybersecurity, PC hardware, and more. I’m currently based in San Francisco, but previously spent over five years in China, covering the country’s technology sector.

Since 2020, I’ve covered the launch and explosive growth of SpaceX’s Starlink satellite internet service, writing 600+ stories on availability and feature launches, but also the regulatory battles over the expansion of satellite constellations, fights with rival providers like AST SpaceMobile and Amazon, and the effort to expand into satellite-based mobile service. I’ve combed through FCC filings for the latest news and driven to remote corners of California to test Starlink’s cellular service.

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