CVE-2026-21509
CVSS v3
7.8
HIGH
EPSS Score
12.5 %
exploit probability
CISA KEV
Yes
known exploited
Exploitation
—
SSVC status
Description
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
CISA Known Exploited Vulnerability
- Date Added
- 2026-01-26
- Patch Due Date
- 2026-02-16
- Ransomware Use
- Unknown
Technical details
- CVSS v3 Vector
- 3.1
- Published
- 2026-01-26
- Last Modified
- 2026-02-11
Frequently asked questions
What is CVE-2026-21509?
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Is CVE-2026-21509 actively exploited?
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 2026-02-16.
What is the CVSS score for CVE-2026-21509?
CVE-2026-21509 has a CVSS v3 base score of 7.8 (HIGH severity), with vector string 3.1.
Is CVE-2026-21509 affecting your environment?
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