CVE-2026-42341 FOSSBilling has an unauthenticated payment bypass via IPN callback forgery
Attackers can bypass payment verification and credit client accounts by forging IPN callbacks when the Custom payment adapter is enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-42341?
CVE-2026-42341 is a critical vulnerability in FOSSBilling, published on 6 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-42341?
How do I fix CVE-2026-42341?
No fix has been published for CVE-2026-42341 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-42341 being exploited?
There is no known exploitation of CVE-2026-42341 in the wild and no public exploit code.
Sources
Also known as GHSA-5493-9m76-2qrr.