# CVE-2021-4138: Server-side request forgery in geckodriver

> GeckoDriver failed to validate Host headers, allowing attackers to bypass restrictions and potentially access internal resources.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 May 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-2h28-m3qw-8www

## What is CVE-2021-4138?

CVE-2021-4138 is a medium-severity server-side request forgery vulnerability in Mozilla geckodriver, published on 2 May 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or the server-specified hostname.

## Which versions are affected by CVE-2021-4138?

It affects 1 product.


Products: Mozilla Geckodriver.

## How do I fix CVE-2021-4138?

No fix has been published for CVE-2021-4138 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-4138 being exploited?

There is no known exploitation of CVE-2021-4138 in the wild and no public exploit code.

## Other vulnerabilities in Mozilla geckodriver

- [CVE-2020-15660](https://insights.sbomify.com/CVE-2020-15660/): Cross-site request forgery in n/a (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-4138 and fix it if it is affected.

What it is: CVE-2021-4138 is a medium-severity server-side request forgery vulnerability in Mozilla geckodriver, published on 2 May 2022. 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-2021-4138 in the wild and no public exploit code.

Affected product: Mozilla geckodriver. 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-2021-4138/ (Markdown: https://insights.sbomify.com/CVE-2021-4138/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4138
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4138
- OSV: https://osv.dev/vulnerability/CVE-2021-4138

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4138/
Summaries are generated and may contain mistakes; the official description above is the record.