# CVE-2021-23422: Arbitrary Code Injection

> Attackers can execute arbitrary OS commands by processing untrusted source files with Inline Tag Command metadata in the bikeshed library.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 16 Aug 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-87cj-px37-rc3x, PYSEC-2021-116, SNYK-PYTHON-BIKESHED-1537646, UBUNTU-CVE-2021-23422

## What is CVE-2021-23422?

CVE-2021-23422 is a high-severity command injection vulnerability in bikeshed, published on 16 Aug 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

This affects the package bikeshed before 3.0.0. This can occur when an untrusted source file containing Inline Tag Command metadata is processed. When an arbitrary OS command is executed, the command output would be included in the HTML output.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)

## Which versions are affected by CVE-2021-23422?

3 open source packages ship an affected version, including bikeshed. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `bikeshed` | PyPI | All versions | 3.0.0 |
| `bikeshed` | PyPI | All versions | 3.0.0 |
| `bikeshed` | PyPI | All versions | 3.0.0 |

Products: Bikeshed Project Bikeshed.

## How do I fix CVE-2021-23422?

Upgrade bikeshed to 3.0.0 or later.

## Is CVE-2021-23422 being exploited?

There is no known exploitation of CVE-2021-23422 in the wild and no public exploit code.

## Other vulnerabilities in bikeshed

- [CVE-2021-23423](https://insights.sbomify.com/CVE-2021-23423/): Directory Traversal (medium 5.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-23422 and fix it if it is affected.

What it is: CVE-2021-23422 is a high-severity command injection vulnerability in bikeshed, published on 16 Aug 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-23422 in the wild and no public exploit code.

Affected packages and fixed versions:
- bikeshed (PyPI): affected all versions; fixed in 3.0.0
- bikeshed (PyPI): affected all versions; fixed in 3.0.0
- bikeshed (PyPI): affected all versions; fixed in 3.0.0

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-2021-23422/ (Markdown: https://insights.sbomify.com/CVE-2021-23422/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-23422
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-23422
- OSV: https://osv.dev/vulnerability/CVE-2021-23422

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-23422/
Summaries are generated and may contain mistakes; the official description above is the record.