CWE-150: Improper Neutralization of Escape, Meta, or Control Sequences

What is Improper Neutralization of Escape, Meta, or Control Sequences?

• Overview: Improper Neutralization of Escape, Meta, or Control Sequences (CWE-150) occurs when software fails to correctly handle special characters in inputs, allowing them to be misinterpreted by downstream systems as control commands instead of data.

• Exploitation Methods:

• Attackers can inject special characters into input fields that are not properly sanitized, causing unintended behavior.
• Common attack patterns include SQL injection, command injection, and Cross-Site Scripting (XSS), where control characters manipulate the flow of data or execution.

• Security Impact:

• Direct consequences include unauthorized command execution, data corruption, or data leakage.
• Potential cascading effects involve compromised system integrity or availability, leading to broader security breaches.
• Business impact may include reputational damage, financial loss due to data breaches, and regulatory penalties.

• Prevention Guidelines:

• Specific code-level fixes include input validation and output encoding to neutralize special characters.
• Security best practices involve adhering to the principle of least privilege and conducting regular security reviews.
• Recommended tools and frameworks: Use input validation libraries, static code analysis tools, and frameworks that provide built-in protection against injection attacks.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

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

function executeCommand(userInput) {
    // Vulnerable code: user input is directly passed to the shell command
    exec(`ls \${userInput}`, (err, stdout, stderr) => {
        if (err) {
            console.error(`Error: \${stderr}`);
        } else {
            console.log(`Output: \${stdout}`);
        }
    });
}

const userInput = process.argv[2];
executeCommand(userInput);

Explanation:

This JavaScript code uses exec to run a shell command, passing user input directly into the command string. This is vulnerable to command injection because an attacker can manipulate the userInput to execute arbitrary commands.

How to fix Improper Neutralization of Escape, Meta, or Control Sequences?

The fix involves using execFile or spawn from the child_process module, which do not spawn a shell by default and take an array of arguments. This prevents shell interpretation of the input. Additionally, validating the input to ensure it matches an expected pattern (e.g., only alphanumeric characters) can further mitigate risks.

Fixed Code Example

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

function executeCommand(userInput) {
    // Validate that the input is a valid directory
    if (!fs.existsSync(userInput) || !fs.lstatSync(userInput).isDirectory()) {
        throw new Error('Invalid directory');
    }

    // Fixed code: Using execFile with arguments array to avoid shell interpretation
    execFile('ls', [userInput], (err, stdout, stderr) => {
        if (err) {
            console.error(`Error: \${stderr}`);
        } else {
            console.log(`Output: \${stdout}`);
        }
    });
}

const userInput = process.argv[2];
executeCommand(userInput);

Explanation:

• Validation: The input is checked to ensure it is a valid directory path. This prevents the execution of commands on invalid or malicious paths.
• ExecFile with Argument Array: Uses execFile with an array of command arguments, thereby avoiding shell interpretation and reducing the risk of injection.
• Error Handling: Introduces error handling for invalid input scenarios, providing feedback if the directory is not valid.