# CVE-2021-27856: FatPipe software administrative account with no password

- Exploited (CISA KEV): no
- Published: 2021-12-15
- CVSS: 9.8 CRITICAL (v3.1)
- EPSS: 5.5% (93th percentile)

FatPipe WARP, IPVPN, and MPVPN software prior to versions 10.1.2r60p91 and 10.2.2r42 includes an account named "cmuser" that has administrative privileges and no password. Older versions of FatPipe software may also be vulnerable. The FatPipe advisory identifier for this vulnerability is FPSA002.

## 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 | 2025-12-03 | 1449 |
| Akamai | No public source | — | — |
| OWASP CRS | Before feed history | — | — |

### F5

- 2025-12-03 · new · rule 200019150
  > Added: signature 200019150 "FatPipe Backdoor Account" (Trojan/Backdoor/Spyware, risk High), systems: Other Web Server. References: CVE-2021-27856.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog

## Our test (measured)

- OWASP Core Rule Set 4.25.0, paranoia level 1, anomaly threshold 5, default CRS settings: passed (0 of 1 requests blocked), template CVE-2021-27856, 2026-11-02
- OWASP Core Rule Set 4.25.0, paranoia level 2, anomaly threshold 5, default CRS settings: blocked (1 of 1 requests blocked), template CVE-2021-27856, 2026-11-02

"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-2021-27856 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2021-27856