# Command Injection (CWE-78)

User input is passed unsanitized to system shell commands, allowing attackers to execute arbitrary commands on the server.

**Stack:** JavaScript

- Prevalence: Common Found in many applications
- Impact: Critical Full server compromise
- Prevention: Avoid shell Use execFile, not exec

**OWASP:** Injection (A03:2021-Injection) - #3

## Description

This could allow attackers to execute unexpected, dangerous commands directly on the operating system. This weakness can lead to a vulnerability in environments in which the attacker does not have direct access to the operating system.

## Prevention

Prevention strategies for OS Command Injection based on 1 Shoulder detection rules.

### JavaScript

Use execFile/spawn with array arguments instead of exec with string commands

## Warning Signs

- [CRITICAL] user input flowing to shell command execution functions

## Consequences

- Execute Unauthorized Commands
- Read Application Data
- Bypass Protection Mechanism

## Mitigations

- Use library calls rather than external processes
- If using Runtime.exec(), use the version that takes an array of arguments
- Use structured mechanisms that automatically enforce separation between data and code

## Detection

- Total rules: 3
- Critical: 3
- Languages: go, javascript, typescript, python

## Rules by Language

### Javascript (1 rules)

- **Command Injection via child_process** [CRITICAL]: Detects user input flowing to shell command execution functions.
  - Remediation: Use execFile() with argument arrays instead of exec() with string commands.

```javascript
const { execFile } = require('child_process');
execFile('ls', ['-la', directory]);
```

Learn more: https://shoulder.dev/learn/javascript/cwe-78/command-injection

### Typescript (1 rules)

- **Command Injection via child_process** [CRITICAL]: Detects user input flowing to shell command execution functions.
  - Remediation: Use execFile() with argument arrays instead of exec() with string commands.

```javascript
const { execFile } = require('child_process');
execFile('ls', ['-la', directory]);
```

Learn more: https://shoulder.dev/learn/javascript/cwe-78/command-injection