CVE-2026-53643 in FOSSBilling
Summary
by MITRE • 07/07/2026
FOSSBilling is a free, open-source billing and client management system. Versions prior to 0.8.0 allow low-privileged staff accounts to perform unauthorized actions via admin API endpoints. The root cause is a combination of the `can_always_access` module flag (which grants all staff access to certain modules) and insufficient permission checks or unsafe parameter handling on individual endpoints. Version 0.8.0 contains a fix. Some workarounds are available. Restrict staff accounts to only those who need access to sensitive settings and/or use a reverse proxy or WAF to restrict access to the affected endpoints to trusted IP addresses or higher-privilege roles.
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Analysis
by VulDB Data Team • 07/07/2026
FOSSBilling represents a critical vulnerability in its pre-0.8.0 versions where low-privileged staff accounts can exploit administrative API endpoints through inadequate permission controls. This flaw stems from the implementation of the `can_always_access` module flag which erroneously grants unrestricted access to sensitive modules regardless of user role or privilege level. The vulnerability manifests when staff members with minimal permissions attempt to interact with administrative functions, bypassing the intended access control mechanisms that should restrict such activities to authorized administrators only.
The technical exploitation occurs through unsafe parameter handling and insufficient validation at individual API endpoints where the system fails to properly verify whether the requesting user possesses adequate privileges before executing sensitive operations. This weakness creates a path for privilege escalation attacks where unauthorized personnel can perform actions typically restricted to higher-privilege accounts including but not limited to user management, system configuration changes, and financial transaction processing. The vulnerability directly maps to CWE-285 Permission Issues and aligns with ATT&CK techniques involving privilege escalation and lateral movement through compromised accounts.
The operational impact of this vulnerability extends beyond simple unauthorized access as it enables potential data manipulation, account takeovers, and system compromise through the exploitation of administrative functions. Attackers could leverage this flaw to modify billing records, manipulate client information, or disrupt service operations while remaining undetected due to the lack of proper logging and monitoring around these privileged actions. Organizations using affected versions face significant risk of financial loss, data breaches, and compliance violations that could result in regulatory penalties and reputational damage.
The remediation for this vulnerability requires immediate implementation of version 0.8.0 which addresses the core permission checking mechanisms and properly validates user privileges before allowing access to administrative functions. Organizations should implement additional defensive measures including strict staff account provisioning policies that limit access to only those personnel who require administrative capabilities for their specific duties. Network-level protections such as reverse proxy configurations or Web Application Firewalls can provide additional layers of defense by restricting direct access to vulnerable endpoints based on IP addresses or requiring higher-privilege authentication tokens before allowing requests to proceed. The fix demonstrates proper adherence to the principle of least privilege and provides a robust foundation for securing administrative interfaces against unauthorized access attempts.