# CVE-2021-41089: `docker cp` allows unexpected chmod of host files

> Attackers can use docker cp to modify host file permissions, potentially widening access to sensitive files on the host system.

- **Severity:** Low 2.8 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Oct 2021
- **Updated:** 4 Aug 2024
- **Also known as:** CLEANSTART-2026-HF26870, DEBIAN-CVE-2021-41089, GHSA-v994-f8vw-g7j4, GO-2024-2913, UBUNTU-CVE-2021-41089, USN-5103-1, openSUSE-SU-2024:11579-1

## What is CVE-2021-41089?

CVE-2021-41089 is a low-severity vulnerability in Fedoraproject Fedora, published on 4 Oct 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Moby is an open-source project created by Docker to enable software containerization. A bug was found in Moby (Docker Engine) where attempting to copy files using `docker cp` into a specially-crafted container can result in Unix file permission changes for existing files in the host’s filesystem, widening access to others. This bug does not directly allow files to be read, modified, or executed without an additional cooperating process. This bug has been fixed in Moby (Docker Engine) 20.10.9. Users should update to this version as soon as possible. Running containers do not need to be restarted.

Weakness: CWE-281 (Improper Preservation of Permissions)

## Which versions are affected by CVE-2021-41089?

4 open source packages ship an affected version, including github.com/docker/docker and github.com/moby/moby. It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/docker/docker` | Go | All versions | 20.10.9 |
| `github.com/docker/docker` | Go | All versions | 20.10.9 |
| `github.com/docker/docker` | Go | All versions | 20.10.9+incompatible |
| `github.com/moby/moby` | Go | All versions | 20.10.9+incompatible |
| `docker` | openSUSE:Tumbleweed | All versions | 20.10.9_ce-1.2 |

Products: Fedoraproject Fedora, Mobyproject Moby.

## How do I fix CVE-2021-41089?

Upgrade github.com/docker/docker to a fixed version for your release line: 20.10.9 or 20.10.9+incompatible.

## Is CVE-2021-41089 being exploited?

There is no known exploitation of CVE-2021-41089 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2024-4577](https://insights.sbomify.com/CVE-2024-4577/): PHP-CGI OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2021-39226](https://insights.sbomify.com/CVE-2021-39226/): Grafana Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2019-5544](https://insights.sbomify.com/CVE-2019-5544/): VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2024-4947](https://insights.sbomify.com/CVE-2024-4947/): Google Chromium V8 Type Confusion (critical 9.6, exploited in the wild)
- [CVE-2024-4671](https://insights.sbomify.com/CVE-2024-4671/): Google Chromium Visuals Use-After-Free (critical 9.6, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-41089 and fix it if it is affected.

What it is: CVE-2021-41089 is a low-severity vulnerability in Fedoraproject Fedora, published on 4 Oct 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-41089 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/docker/docker (Go): affected all versions; fixed in 20.10.9
- github.com/docker/docker (Go): affected all versions; fixed in 20.10.9
- github.com/docker/docker (Go): affected all versions; fixed in 20.10.9+incompatible
- github.com/moby/moby (Go): affected all versions; fixed in 20.10.9+incompatible

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-2021-41089/ (Markdown: https://insights.sbomify.com/CVE-2021-41089/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-41089
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-41089
- OSV: https://osv.dev/vulnerability/CVE-2021-41089

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-41089/
Summaries are generated and may contain mistakes; the official description above is the record.