CVE-2026-21509
CISA KEVPublished January 26, 2026 · Updated April 3, 2026
high
Official Description+
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.
Affected Products
| Vendor | Product |
|---|---|
| Microsoft | Office |
Patch Status
Patch by 2026-02-16
Recommended Actions
- Check if your systems use any of the affected products listed above.
- Apply vendor patches immediately if available.
- This vulnerability is in CISA's Known Exploited Vulnerabilities catalog — prioritize remediation.
- Monitor vendor advisories for updates and additional mitigations.
- Review logs for indicators of compromise related to CVE-2026-21509.