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OpenAdvisories
High · 7.8 Known exploited Public exploit CVE-2026-21509 EUVD-2026-4666GHSA-ch84-h92g-mw93

Microsoft Office Security Feature Bypass Vulnerability

Published Jan 26, 2026 · Updated Jul 30, 2026 · Assigned by microsoft

Vendor: Microsoft Product: Microsoft 365 Apps for Enterprise Product: Microsoft Office 2016 Product: Microsoft Office 2019 Product: Microsoft Office LTSC 2021 Product: Microsoft Office LTSC 2024

Description

Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.

Affected products

VendorProductAffectedFixed
Microsoft Microsoft 365 Apps for Enterprise 16.0.1 – < https://aka.ms/OfficeSecurityReleases https://aka.ms/OfficeSecurityReleases
Microsoft Microsoft Office 2016 16.0.0 – < 16.0.5539.1001 16.0.5539.1001
Microsoft Microsoft Office 2019 19.0.0 – < 16.0.10417.20095 16.0.10417.20095
Microsoft Microsoft Office LTSC 2021 16.0.1 – < https://aka.ms/OfficeSecurityReleases https://aka.ms/OfficeSecurityReleases
Microsoft Microsoft Office LTSC 2024 16.0.0 – < https://aka.ms/OfficeSecurityReleases https://aka.ms/OfficeSecurityReleases

Public exploits

Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.

Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.

GitHub 13 repositories · most starred shown

Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.

Advisories 3

References