# CVE-2026-61500: Rejetto HFS < 3.2.1 Session Forgery via Predictable Signing Key

- Exploited (CISA KEV): no
- Published: 2026-07-13
- CVSS: 9.3 CRITICAL (v4.0)
- EPSS: 1.9% (80th percentile)
- CWE: CWE-338

Rejetto HFS 3.0.0 through 3.2.0 derives its session-cookie signing key from the non-cryptographic Math.random() generator and discloses outputs of the same generator to unauthenticated clients during login. A remote attacker can collect a small number of login responses, reconstruct the generator's state, recover the signing key, and forge a valid administrator session cookie, leading to full administrative access and remote code execution via the server_code configuration feature.

## 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 | Rule published | 2026-10-21 | 100 |
| Akamai | No public source | — | — |
| OWASP CRS | No public claim | — | — |

### F5

- 2026-10-21 · new · rule 200204110
  > Added: signature 200204110 "Rejetto HFS Remote Code Execution (2)" (Server Side Code Injection, risk High), systems: Microsoft Windows, Other Web Server. References: CVE-2026-61500.
  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-2026-61500 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2026-61500