# CVE-2026-40495: FOSSBilling version exposed via asset cache buster

> Unauthenticated attackers can determine the exact FOSSBilling version via asset cache buster parameters, bypassing version hiding settings to facilitate targeted attacks.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/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:** 3 Jun 2026
- **Updated:** 4 Jun 2026
- **Also known as:** GHSA-gqcp-g7rm-p5v6

## What is CVE-2026-40495?

CVE-2026-40495 is a medium-severity vulnerability in FOSSBilling, published on 3 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. Versions prior to 0.8.0 leak the exact system version through asset cache buster parameters in HTML output, bypassing the `hide_version_public` security setting. The FOSSBilling version is embedded in the query string of every `<script>` and `<link>` tag generated by the `script_tag` and `stylesheet_tag` Twig filters. This information is visible to all visitors — including unauthenticated guests — on every page, regardless of whether the `hide_version_public` setting is enabled.  The `X-FOSSBilling-Version` HTTP header and the `guest.system.version` API endpoint correctly honour the `hide_version_public` setting, but the asset cache buster parameters were overlooked. Knowledge of the exact FOSSBilling version makes it significantly easier for malicious actors to identify known vulnerabilities applicable to a given installation and craft targeted exploits. While not a direct vulnerability on its own, it undermines the intended protection offered by the `hide_version_public` setting and facilitates reconnaissance. Version 0.8.0 contains a patch. There is no practical workaround that removes the version from asset URLs without modifying source code.

Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2026-40495?


## How do I fix CVE-2026-40495?

No fix has been published for CVE-2026-40495 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-40495 being exploited?

There is no known exploitation of CVE-2026-40495 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40495 and fix it if it is affected.

What it is: CVE-2026-40495 is a medium-severity vulnerability in FOSSBilling, published on 3 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-2026-40495 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-2026-40495/ (Markdown: https://insights.sbomify.com/CVE-2026-40495/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40495
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40495
- OSV: https://osv.dev/vulnerability/CVE-2026-40495

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40495/
Summaries are generated and may contain mistakes; the official description above is the record.