CVE-2026-53648

FOSSBilling from 0.1.0 until 0.8.7 has a path traversal vulnerability in the unauthenticated api/guest/system/template_exists endpoint because templateExists uses Path::join on the attacker-controlled file parameter without rejecting .. sequences or verifying the resolved path stays inside the active theme directory. An attacker can determine whether arbitrary files or directories exist on the server.

In FOSSBilling from 0.8.4 until 0.8.6, hasManagePermission fails open for inactive non-core modules, skipping access checks. A low-privileged staff account can read decrypted extension secrets and overwrite stored configuration of a deactivated module.

FOSSBilling versions 0.6.0 through 0.7.2 have an unauthenticated payment bypass vulnerability. An attacker can mark any unpaid invoice as paid and credit the client account by sending a single crafted HTTP request to the IPN callback endpoint.

FOSSBilling versions 0.7.2 and prior have a vulnerability in the guest API that allows the creation of new administrator accounts even when one already exists. A flaw in the admin existence check enables an attacker to bypass protections.

FOSSBilling prior to version 0.8.0 has a Server-Side Template Injection (SSTI) vulnerability in the template rendering system. Administrators can inject arbitrary Twig expressions, leading to information disclosure and remote code execution.

FOSSBilling versions 0.5.4 to 0.8.0 have an authorization bypass in API role handling, allowing unauthenticated access to privileged `/api/system/*` endpoints. Attackers can invoke admin API methods without valid credentials.

FOSSBilling from 0.1.0 until 0.8.7 has an unauthenticated POST /api/guest/client/create endpoint that reveals whether a submitted email belongs to a registered client by returning a distinct unredacted error. An attacker can compare responses to determine if an email belongs to an existing client.

In FOSSBilling versions 0.5.3 through 0.7.2, the Guest `serviceapikey/get_info` API endpoint is accessible without authentication. Any caller with a valid API key can retrieve all custom configuration parameters (`custom_*` fields) stored in the key's database record.

In FOSSBilling versions 0.5.6 through 0.7.2, when a client requests a password reset multiple times, the system reuses the existing token instead of generating a new one, with the 15-minute validity anchored to the first request. An attacker who obtained the original reset link can still use it even after the victim requests a new reset, as the original token is never invalidated.

FOSSBilling prior to version 0.8.0 contains a vulnerability that allows a low-privileged staff account to escalate privileges via the admin API. A user with the `staff.create_and_edit_staff` permission can call `/api/admin/staff/permissions_update` for their own account and set any permissions, bypassing role-based access control.