# CVE-2026-43920: FOSSBilling: Unauthenticated update patcher endpoint allows remote maintenance execution

> Unauthenticated attackers can trigger privileged maintenance operations via the /run-patcher endpoint, causing denial of service and data modification.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/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:** 25 Jun 2026
- **Updated:** 26 Jun 2026
- **Also known as:** GHSA-prx6-m547-rfmg

## What is CVE-2026-43920?

CVE-2026-43920 is a medium-severity missing authorization vulnerability in FOSSBilling, published on 25 Jun 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. In versions 0.5.4 through 0.7.2, the /run-patcher maintenance endpoint in FOSSBilling was accessible without authentication, which allowed unauthenticated remote users to trigger update patch routines that modify configuration files, execute database schema changes, perform filesystem mutations, and clear caches. The /run-patcher endpoint executes privileged maintenance operations - configuration migrations, database patch execution (including ALTER TABLE, DROP TABLE, UPDATE statements), filesystem deletions and renames, and cache clearing - without requiring administrator authentication, CSRF validation, or CLI context. An unauthenticated remote attacker can trigger these operations by sending a simple HTTP GET request to /run-patcher, which can be abused for denial-of-service attacks. Certain patches (e.g., batch token regeneration for all admin and client accounts in patch 53, and session invalidation) are disruptive even when re-executed against an already-patched instance. Repeated or concurrent requests may also cause inconsistent database state. This issue has been fixed in version 0.8.0.

Weakness: CWE-306 (Missing Authentication for Critical Functionality)

## Which versions are affected by CVE-2026-43920?


## How do I fix CVE-2026-43920?

No fix has been published for CVE-2026-43920 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-43920 being exploited?

There is no known exploitation of CVE-2026-43920 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43920 and fix it if it is affected.

What it is: CVE-2026-43920 is a medium-severity missing authorization vulnerability in FOSSBilling, published on 25 Jun 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-2026-43920 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-2026-43920/ (Markdown: https://insights.sbomify.com/CVE-2026-43920/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43920
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43920
- OSV: https://osv.dev/vulnerability/CVE-2026-43920

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43920/
Summaries are generated and may contain mistakes; the official description above is the record.