---
cve: "CVE-2026-27604"
severity: "CRITICAL"
cvss: 10.0
epss: "1.3%"
vendor: "fossbilling"
kev: false
exploited: false
published: "2026-06-23 14:25:20"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-11-07T13:48:38+01:00"
---

# CVE-2026-27604

> 10.0 CRITICAL · 🧪 PoC

## Beschreibung

FOSSBilling is a free, open-source billing and client management system. Starting in version 0.5.4 and prior to version 0.8.0, an authorization bypass in the API role handling allows unauthenticated access to privileged `/api/system/*` endpoints. Because `system` resolves to the cron admin identity, attackers can invoke admin API methods without valid credentials, session, or CSRF token. Version 0.8.0 patches the issue. Some workarounds are available. Block external access to `/api/system/*` at reverse proxy/WAF, restrict API access by trusted source IPs only (`api.allowed_ips`), rotate all admin/client API tokens immediately, invalidate active sessions and reset high-privilege credentials, and/or review API request logs for suspicious `/api/system/` access and treat as potential incident.

## CNA-Record (Kanon, cvelistV5)

- CNA: **GitHub_M**
- State: PUBLISHED
- Stand: 2026-06-23 15:11:21
- CNA-CVSS: **10.0** (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **none**
  - Automatable: **yes**
  - Technical Impact: **total**

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Schwachstellen-Klasse

- **CWE-200** — Exposure of Sensitive Information to an Unauthorized Actor
  The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
- **CWE-306** — Missing Authentication for Critical Functionality
  The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
- **CWE-862** — Missing Authorization
  The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
- **CWE-863** — Incorrect Authorization
  The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

## Angriffsmuster (CAPEC)

- [CAPEC-13 — Subverting Environment Variable Values](https://capec.mitre.org/data/definitions/13.html) _(Severity: Very High)_
- [CAPEC-22 — Exploiting Trust in Client](https://capec.mitre.org/data/definitions/22.html) _(Severity: High)_
- [CAPEC-116 — Excavation](https://capec.mitre.org/data/definitions/116.html) _(Severity: Medium)_
- [CAPEC-169 — Footprinting](https://capec.mitre.org/data/definitions/169.html) _(Severity: Very Low)_
- [CAPEC-224 — Fingerprinting](https://capec.mitre.org/data/definitions/224.html) _(Severity: Very Low)_
- [CAPEC-285 — ICMP Echo Request Ping](https://capec.mitre.org/data/definitions/285.html) _(Severity: Low)_
- [CAPEC-287 — TCP SYN Scan](https://capec.mitre.org/data/definitions/287.html) _(Severity: Low)_
- [CAPEC-290 — Enumerate Mail Exchange (MX) Records](https://capec.mitre.org/data/definitions/290.html) _(Severity: Low)_

## ATT&CK-Techniken

- [T1562.003 — Impair Defenses:Impair Command History Logging](https://attack.mitre.org/techniques/T1562/003/)
- [T1574.006 — Hijack Execution Flow:Dynamic Linker Hijacking](https://attack.mitre.org/techniques/T1574/006/)
- [T1574.007 — Hijack Execution Flow:Path Interception by PATH Environment ](https://attack.mitre.org/techniques/T1574/007/)
- [T1217 — Browser Bookmark Discovery](https://attack.mitre.org/techniques/T1217/)
- [T1592 — Gather Victim Host Information](https://attack.mitre.org/techniques/T1592/)
- [T1595 — Active Scanning](https://attack.mitre.org/techniques/T1595/)

## Patch verfügbar (OSV)

- 3bd35f5b2921d8a26a403142ae0408f95e6463cc (Commit)

## Referenzen

- <https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-78x5-c8gw-8279>
- <https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-57mv-jm88-66jc>
- <https://www.vulncheck.com/blog/fossbilling-auth-bypass-ssti-rce>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-27604/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_