FOSSBilling up to 0.7.2 IPN ipn.php improper authentication

Summaryinfo

A vulnerability was found in FOSSBilling up to 0.7.2. It has been declared as critical. The affected element is an unknown function of the file ipn.php of the component IPN Handler. The manipulation results in improper authentication. This vulnerability is identified as CVE-2026-42341. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability, which was classified as critical, was found in FOSSBilling up to 0.7.2. Affected is some unknown processing of the file ipn.php of the component IPN Handler. The manipulation with an unknown input leads to a improper authentication vulnerability. CWE is classifying the issue as CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

FOSSBilling is a free, open-source billing and client management system. Versions 0.6.0 through 0.7.2 have an unauthenticated payment bypass vulnerability in FOSSBilling's IPN callback endpoint. When the Custom payment adapter is enabled, an attacker can mark any unpaid invoice as paid and credit the associated client account without making an actual payment, by sending a single crafted HTTP request. Version 0.8.0 patches the issue. Some workarounds are available. Disable the Custom payment gateway if not actively needed and/or restrict access to `/ipn.php` at the web server level (e.g., via IP allowlisting), noting that this may interfere with legitimate payment callback processing.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-42341 since 04/26/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available.

By approaching the search of inurl:ipn.php it is possible to find vulnerable targets with Google Hacking.

Upgrading to version 0.8.0 eliminates this vulnerability.

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Productinfo

Type

• Billing Software

Name

• FOSSBilling

Version

• 0.7.0
• 0.7.1
• 0.7.2

Website

• Product: https://github.com/FOSSBilling/FOSSBilling/

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