# CVE-2025-53521: F5 BIG-IP Stack-Based Buffer Overflow Vulnerability

- Exploited (CISA KEV): yes, added 2026-03-27
- Published: 2025-10-15
- CVSS: 9.3 CRITICAL (v4.0)
- EPSS: 2.3% (83th percentile)
- CWE: CWE-121

When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code Execution (RCE).  

Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

## 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-2025-53521 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2025-53521