# CVE-2021-42740: Improper Neutralization of Special Elements used in a Command in Shell-quote

> Attackers can execute arbitrary commands via shell metacharacters in the shell-quote Node.js library due to a flawed regex.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Oct 2021
- **Updated:** 4 Aug 2024
- **Also known as:** CLSA-2026-1773879463, DEBIAN-CVE-2021-42740, GHSA-g4rg-993r-mgx7, ROOT-APP-NPM-CVE-2021-42740, UBUNTU-CVE-2021-42740

## What is CVE-2021-42740?

CVE-2021-42740 is a critical command injection vulnerability in n/a, published on 21 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The shell-quote package before 1.7.3 for Node.js allows command injection. An attacker can inject unescaped shell metacharacters through a regex designed to support Windows drive letters. If the output of this package is passed to a real shell as a quoted argument to a command with exec(), an attacker can inject arbitrary commands. This is because the Windows drive letter regex character class is {A-z] instead of the correct {A-Za-z]. Several shell metacharacters exist in the space between capital letter Z and lower case letter a, such as the backtick character.

Weakness: CWE-77 (Improper Neutralization of Special Elements used in a Command)

## Which versions are affected by CVE-2021-42740?

2 open source packages ship an affected version, including shell-quote. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `shell-quote` | npm | From 1.6.3 | 1.7.3 |
| `shell-quote` | npm | From 1.6.3 | 1.7.3 |

Products: Shell-Quote Project Shell-Quote.

## How do I fix CVE-2021-42740?

Upgrade shell-quote to 1.7.3 or later.

## Is CVE-2021-42740 being exploited?

There is no known exploitation of CVE-2021-42740 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2016-10541](https://insights.sbomify.com/CVE-2016-10541/): Potential Command Injection in shell-quote (critical 9.8)
- [CVE-2026-13311](https://insights.sbomify.com/CVE-2026-13311/): shell-quote parse() is quadratic in token count, enabling denial of service (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-42740 and fix it if it is affected.

What it is: CVE-2021-42740 is a critical command injection vulnerability in n/a, published on 21 Oct 2021. 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-2021-42740 in the wild and no public exploit code.

Affected packages and fixed versions:
- shell-quote (npm): affected from 1.6.3; fixed in 1.7.3
- shell-quote (npm): affected from 1.6.3; fixed in 1.7.3

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-2021-42740/ (Markdown: https://insights.sbomify.com/CVE-2021-42740/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-42740
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-42740
- OSV: https://osv.dev/vulnerability/CVE-2021-42740

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-42740/
Summaries are generated and may contain mistakes; the official description above is the record.