# CVE-2021-39947: Information disclosure in GitLab Runner

> Attackers can read sensitive data from other jobs due to trace file buffer reuse mixing outputs in GitLab Runner.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 Jun 2022
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-hwx9-v7rw-v3qm, UBUNTU-CVE-2021-39947

## What is CVE-2021-39947?

CVE-2021-39947 is a medium-severity vulnerability in GitLab Runner, published on 6 Jun 2022. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

In specific circumstances, trace file buffers in GitLab Runner versions up to 14.3.4, 14.4 to 14.4.2, and 14.5 to 14.5.2 would re-use the file descriptor 0 for multiple traces and mix the output of several jobs

## Which versions are affected by CVE-2021-39947?

It affects 1 product.


Products: Gitlab Gitlab Runner.

## How do I fix CVE-2021-39947?

No fix has been published for CVE-2021-39947 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-39947 being exploited?

There is no known exploitation of CVE-2021-39947 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-39947 and fix it if it is affected.

What it is: CVE-2021-39947 is a medium-severity vulnerability in GitLab Runner, published on 6 Jun 2022. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-39947 in the wild and no public exploit code.

Affected product: GitLab Runner. 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-2021-39947/ (Markdown: https://insights.sbomify.com/CVE-2021-39947/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-39947
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-39947
- OSV: https://osv.dev/vulnerability/CVE-2021-39947

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-39947/
Summaries are generated and may contain mistakes; the official description above is the record.