CVSS v3
7.8
HIGH
EPSS Score
12.5%
exploit probability
CISA KEV
Yes
known exploited
Exploitation
—
SSVC status
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Yes. CVE-2026-21509 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning it has been confirmed as actively exploited in the wild. CISA requires federal agencies to patch by 2/16/2026.
CVE-2026-21509 has a CVSS v3 base score of 7.8 (HIGH severity), with vector string 3.1.
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Ranked by exploit probability (EPSS).