CWE-88: Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')

What is Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')?

• Overview: Improper Neutralization of Argument Delimiters in a Command ('Argument Injection') occurs when a software application constructs command strings for external components without securely handling delimiters like spaces or special characters, allowing unintended arguments to be processed.

• Exploitation Methods:

• Attackers can inject additional arguments by manipulating input fields that are used to construct command strings.
• Common attack patterns include adding unexpected switches or flags to command lines, potentially altering the command's behavior.

• Security Impact:

• Direct consequences include unauthorized command execution or behavior changes in the software.
• Potential cascading effects could involve data leaks, privilege escalation, or system compromise.
• Business impact may involve data breaches, service disruptions, or damage to reputation.

• Prevention Guidelines:

• Use parameterized APIs or functions that handle command execution to separate code logic from data.
• Validate and sanitize all inputs rigorously to ensure injected delimiters can't alter command structure.
• Employ tools and frameworks that abstract command execution and manage input handling securely.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific, PHP

Affected Technologies: Not specified

Vulnerable Code Example

Certainly! Let's refine the code examples to ensure they demonstrate the vulnerability and fix clearly, with proper formatting and explanations.

const { exec } = require('child_process');

function executeCommand(userInput) {
    // Vulnerable code: directly concatenating user input into a command string
    const command = 'ls ' + userInput;  // User input is not sanitized, leading to potential command injection
    exec(command, (error, stdout, stderr) => {
        if (error) {
            console.error(`Error: \${error.message}`);
            return;
        }
        console.log(`Output: \${stdout}`);
    });
}

const userInput = process.argv[2];  // Taking input from command line arguments
executeCommand(userInput);

Explanation:

• The above JavaScript code uses exec from the child_process module to execute system commands.
• It concatenates user input directly into the command string without proper validation or sanitization.
• This approach is vulnerable to argument injection attacks, where a malicious user could input dangerous shell commands, potentially compromising the system.

How to fix Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')?

Fixed Code Example

const { execFile } = require('child_process');

function executeCommand(userInput) {
    // Fixed code: using execFile to safely pass arguments
    execFile('ls', [userInput], (error, stdout, stderr) => {
        if (error) {
            console.error(`Error: \${error.message}`);
            return;
        }
        console.log(`Output: \${stdout}`);
    });
}

const userInput = process.argv[2];  // Taking input from command line arguments
executeCommand(userInput);

Explanation:

• The execFile function is used instead of exec, which allows us to pass the command and its arguments as separate elements in an array.
• This method does not interpret spaces and special characters as shell metacharacters, preventing command injection.
• By treating each argument as a separate entity, execFile ensures that user input cannot alter the command structure, significantly reducing the risk of injection attacks.
• This approach is a best practice for executing commands with user-provided input in Node.js applications.