CVE-2026-42341: 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 call
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.
Details
Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-42341
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-423410.18% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 8% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-42341 | coverage & exploitation status | NVD · CVE.org |
Recent advisories for FOSSBilling is a
A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.
- unknownCVE-2026-53648: FOSSBilling is a free, open-source billing and client management system. Prior to version 0.8.…nvd · 2026-07-07
- unknownCVE-2026-53647: FOSSBilling is a free, open-source billing and client management system. In versions 0.5.3 thr…nvd · 2026-07-07
- unknownCVE-2026-53646: FOSSBilling is a free, open-source billing and client management system. In versions 0.5.6 thr…nvd · 2026-07-06
- unknownCVE-2026-53645: FOSSBilling is a free, open-source billing and client management system. Versions prior to 0.8…nvd · 2026-07-06
- unknownCVE-2026-53644: FOSSBilling is a free, open-source billing and client management system. Versions 0.5.3 throug…nvd · 2026-07-06
- unknownCVE-2026-53643: FOSSBilling is a free, open-source billing and client management system. Versions prior to 0.8…nvd · 2026-07-06
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