CVE-2026-21509
HIGH severity · CVSS 7.8 · CWE-807 · actively exploited (CISA KEV)
7.8CVSS HIGH exploited
Actively exploited in the wild (CISA Known Exploited Vulnerabilities).
Added to KEV 2026-01-26. US federal agencies must patch by 2026-02-16.
Summary
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Impact & exploitability
Attack vectorLocal
Attack complexityLow
Privileges requiredNone
User interactionRequired
Confidentiality impactHigh
Integrity impactHigh
Availability impactHigh
Exploit probability (EPSS)72%
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Affected products we track (1)
Recommendation
This vulnerability is being actively exploited in the wild — patch affected products urgently. Open any affected product above for its exact safe version.
Additional information
- NVD record
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509Advisory
- https://www.vicarius.io/vsociety/posts/cve-2026-21509-mitigation-script-microsoft-office-security-feature-bypass-vulnerabilityAdvisory
- https://www.vicarius.io/vsociety/posts/cve-2026-21509-detection-script-microsoft-office-security-feature-bypass-vulnerabilityAdvisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21509