Oct 19, 2026 · 16:58 UTC SEARCH
UNRATED KNOWN EXPLOITED
Vulnerability intelligence

CVE-2026-21509

VendorMicrosoft
ProductOffice
Known exploitedYes
Added to CISA KEVJanuary 26, 2026
KEV due dateFebruary 16, 2026
Known ransomware useNot identified by CISA

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.

Required action

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

CISA KEV status

This vulnerability is listed in CISA’s Known Exploited Vulnerabilities Catalog. Known ransomware campaign use: Unknown.

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