# CVE-2020-27534: Path Traversal in Moby builder

> Docker Engine allows local attackers to execute arbitrary code or escalate privileges via path traversal in binfmt_misc checks.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 30 Dec 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-6hwg-w5jg-9c6x

## What is CVE-2020-27534?

CVE-2020-27534 is a medium-severity path traversal vulnerability in n/a, published on 30 Dec 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

util/binfmt_misc/check.go in Builder in Docker Engine before 19.03.9 calls os.OpenFile with a potentially unsafe qemu-check temporary pathname, constructed with an empty first argument in an ioutil.TempDir call.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2020-27534?

4 open source packages ship an affected version, including github.com/docker/docker and github.com/moby/moby. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/docker/docker` | Go | All versions | 19.03.9 |
| `github.com/docker/docker` | Go | All versions | 19.03.9 |
| `github.com/moby/moby` | Go | All versions | 19.03.9 |
| `github.com/moby/moby` | Go | All versions | 19.03.9 |

Products: Docker Docker.

## How do I fix CVE-2020-27534?

Upgrade github.com/docker/docker to 19.03.9 or later.

## Is CVE-2020-27534 being exploited?

There is no known exploitation of CVE-2020-27534 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2014-9357](https://insights.sbomify.com/CVE-2014-9357/): Arbitrary Code Execution (critical 10.0)
- [CVE-2020-14298](https://insights.sbomify.com/CVE-2020-14298/): Privilege escalation in Docker (high 8.8)
- [CVE-2020-14300](https://insights.sbomify.com/CVE-2020-14300/): Privilege escalation in Docker (high 8.8)
- [CVE-2018-15514](https://insights.sbomify.com/CVE-2018-15514/): Deserialization in n/a (high 8.8)
- [CVE-2014-9356](https://insights.sbomify.com/CVE-2014-9356/): Path Traversal in Docker (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-27534 and fix it if it is affected.

What it is: CVE-2020-27534 is a medium-severity path traversal vulnerability in n/a, published on 30 Dec 2020. 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-2020-27534 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/docker/docker (Go): affected all versions; fixed in 19.03.9
- github.com/docker/docker (Go): affected all versions; fixed in 19.03.9
- github.com/moby/moby (Go): affected all versions; fixed in 19.03.9
- github.com/moby/moby (Go): affected all versions; fixed in 19.03.9

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-2020-27534/ (Markdown: https://insights.sbomify.com/CVE-2020-27534/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-27534
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-27534
- OSV: https://osv.dev/vulnerability/CVE-2020-27534

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-27534/
Summaries are generated and may contain mistakes; the official description above is the record.