Microsoft Office Security Feature Bypass Vulnerability

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• NewsExploited · CISA KEVMicrosoft · Office

  Microsoft Office Security Feature Bypass Vulnerability

  CVE-2026-21509

  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.

  CISA's required action · due 16 Feb 2026 for U.S. federal civilian agencies

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

  Cited by CISA: msrc.microsoft.com · nvd.nist.gov

  Added to KEV 26 Jan 2026 · Source checked 4 Nov 2026, 16:40 UTC · CISA KEV entry

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