CVE-2026-27604 FOSSBilling: Improper API Role Validation (system) Enables Unauthenticated Access to Privileged Admin Functions
Unauthenticated attackers can access privileged admin API endpoints in FOSSBilling due to improper role validation, allowing unauthorized system control.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-27604?
CVE-2026-27604 is a critical missing authorization vulnerability in FOSSBilling, published on 23 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-27604?
How do I fix CVE-2026-27604?
No fix has been published for CVE-2026-27604 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-27604 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27604 exists.
Public exploit code: 1 Nuclei template.