CVSS 3.1
7.8 highCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HCVE-2026-21509
High (7.8) in Microsoft Office. In CISA KEV since 2026-01-26. EPSS 71% chance of exploitation in the next 30 days.
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Severity
- EPSS
- 71% chance of exploitation in the next 30 days; higher than 99% of CVEs (scores of 2026-10-31)
- CISA KEV
- listed 2026-01-26, due 2026-02-16
- CWE
- CWE-807
- Published
- Modified
- Record from
- the NVD, synced
Affected
- microsoft:365_apps
- microsoft:office
- microsoft:office_long_term_servicing_channel
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509
- https://www.vicarius.io/vsociety/posts/cve-2026-21509-detection-script-microsoft-office-security-feature-bypass-vulnerability
- https://www.vicarius.io/vsociety/posts/cve-2026-21509-mitigation-script-microsoft-office-security-feature-bypass-vulnerability
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21509