# 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.

- **Severity:** Critical 9.2 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 Jul 2026
- **Updated:** 7 Jul 2026
- **Also known as:** GHSA-5493-9m76-2qrr

## 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.

Weakness: CWE-346 (Origin Validation Error), CWE-306 (Missing Authentication for Critical Functionality)

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42341 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-42341 in the wild and no public exploit code.

Affected product: FOSSBilling. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-42341/ (Markdown: https://insights.sbomify.com/CVE-2026-42341/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42341
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42341
- OSV: https://osv.dev/vulnerability/CVE-2026-42341

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42341/
Summaries are generated and may contain mistakes; the official description above is the record.