# CVE-2021-42756: Fortinet FortiWeb

- Exploited (CISA KEV): no
- Published: 2023-02-16
- CVSS: 9.3 CRITICAL (v3.1)
- EPSS: 35.2% (98th percentile)
- CWE: CWE-121

Multiple stack-based buffer overflow vulnerabilities [CWE-121] in the proxy daemon of FortiWeb 5.x all versions, 6.0.7 and below, 6.1.2 and below, 6.2.6 and below, 6.3.16 and below, 6.4 all versions may allow an unauthenticated remote attacker to achieve arbitrary code execution via specifically crafted HTTP requests.

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

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | Before feed history | — | — |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | Before feed history | — | — |
| Fastly | Before feed history | — | — |
| F5 | Rule published | 2023-05-09 | 82 |
| Akamai | No public source | — | — |
| OWASP CRS | No public claim | — | — |

### F5

- 2023-05-09 · new · rule 200011090
  > Added: signature 200011090 "FortiWeb Stack-based Buffer Overflow" (Buffer Overflow, risk High), systems: Other Web Server. References: CVE-2021-42756.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog

"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-2021-42756 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2021-42756