CVE-2026-27604

FOSSBilling: Improper API Role Validation (system) Enables Unauthenticated Access to Privileged Admin Functions

State: Published
Severity: 10.0 Critical
Published: Jun 23, 2026
Updated: Jun 23, 2026
Reserved: Feb 20, 2026

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.

Scores

CVSS	Score	Vector	Source
4.0	10.0 Critical	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	GitHub_M

Weaknesses

CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
CWE-306 Missing Authentication for Critical Function
CWE-862 Missing Authorization
CWE-863 Incorrect Authorization

Affected Products

Product	Versions
FOSSBillingFOSSBilling	>= 0.5.4, < 0.8.0Affected

References

Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.