CVE-2026-42331
HighCVSS 7.7Exploitation Probability (EPSS)
Low risk16th percentile - higher than 16% of all known CVEs
Summary
In FOSSBilling prior to version 0.8.0, the Guest API invoice/update endpoint lacks an authorization check, allowing an unauthenticated user with knowledge of an invoice hash to modify the payment gateway for an unpaid invoice. An attacker who obtains the hash (e.g., via shared URLs, referrer headers, or email links) can change the `gateway_id` to any configured payment gateway.
Risk Assessment
The risk involves potential redirection of payments to a different gateway, which could lead to financial loss or payment disruption. The attack is limited by the need for the invoice hash and the requirement that the gateway must already be installed and configured by an administrator.
Recommendation
Upgrade FOSSBilling to version 0.8.0 or later, which includes the fix. No known workarounds are available.
Original NVD description (English source)
FOSSBilling is a free, open-source billing and client management system. Prior to version 0.8.0, the Guest API invoice/update endpoint is missing an authorization check present in other invoice-related endpoints, allowing an unauthenticated user with knowledge of an invoice hash to modify the payment gateway associated with an unpaid invoice. An attacker who obtains an invoice hash, which may leak through shared URLs, referrer headers, or email links, can change the `gateway_id` on an unpaid invoice to any payment gateway configured in the system. This does not allow redirecting payments to an arbitrary external endpoint, as the gateway must already be installed and configured by an administrator. The practical impact is further limited by the `invoice_accessible_from_hash` system setting. Version 0.8.0 contains a patch. No known workarounds are available.