# CVE-2026-21509: Microsoft Office Security Feature Bypass Vulnerability

- Exploited (CISA KEV): yes, added 2026-01-26
- Published: 2026-01-26
- CVSS: 7.8 HIGH (v3.1)
- EPSS: 70.8% (99th percentile)
- CWE: CWE-807

Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | No public claim | — | — |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | No public claim | — | — |
| Fastly | Before feed history | — | — |
| F5 | No public claim | — | — |
| Akamai | No public source | — | — |
| OWASP CRS | No public claim | — | — |

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2026-21509 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2026-21509