CVE-2026-21509: Microsoft Office Security Feature Bypass Vulnerability

Required action (CISA's text)

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Description (NVD)

Microsoft Office contains a security feature bypass vulnerability in which reliance on untrusted inputs in a security decision in Microsoft Office could allow an unauthorized attacker to bypass a security feature locally. Some of the impacted product(s) could be end-of-life (EoL) and/or end-of-service (EoS). Users are advised to discontinue use and/or transition to a supported version.

SOURCES

• CISA KEVCISA Known Exploited Vulnerabilities catalog

Other Microsoft flaws

• patchtuesday:2026-11: Vulnerability in Microsoft
• CVE-2026-124194: Microsoft Office Outlook Missing User Interaction for Potentially Unsafe Action Vulnerability
• CVE-2026-96951: Microsoft Windows Command Injection Vulnerability
• CVE-2026-65660: Microsoft SharePoint Code Injection Vulnerability
• CVE-2026-85880: Microsoft Windows Heap-Based Buffer Overflow Vulnerability

Data from NVD, CISA KEV, FIRST EPSS and vendor advisories. Updated 10 Nov 2026.