CWE-146: Improper Neutralization of Expression/Command Delimiters

What is Improper Neutralization of Expression/Command Delimiters?

• Overview:

• CWE-146 refers to a vulnerability where software fails to adequately neutralize or sanitize special characters that serve as expression or command delimiters. This can lead to unintended commands or expressions being executed when input data is processed.

• Exploitation Methods:

• Attackers can exploit this vulnerability by injecting malicious input that includes special characters or delimiters, which the application may misinterpret as commands or expressions.
• Common attack patterns include command injection, SQL injection, and any other input-based attacks where the injection of delimiters alters the intended execution flow.

• Security Impact:

• Direct consequences include unauthorized command execution, data leakage, data corruption, and system compromise.
• Potential cascading effects involve privilege escalation, persistent backdoor installation, and further penetration into the network.
• Business impact can range from operational disruption to significant financial loss, reputational damage, and legal liabilities.

• Prevention Guidelines:

• Specific code-level fixes include implementing stringent input validation and sanitization routines to ensure all inputs are correctly neutralized.
• Security best practices involve using parameterized queries, prepared statements, and input escaping functions to mitigate the risk of injection.
• Recommended tools and frameworks include using static and dynamic analysis tools to detect vulnerabilities, adopting secure coding libraries, and employing runtime protection solutions to monitor and block injection attempts.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

Certainly! Below is the improved content with the necessary corrections and enhancements:

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

function executeCommand(userInput) {
    // Vulnerable: Directly embedding user input into a shell command
    // This allows for command injection if userInput contains shell delimiters
    exec('echo ' + userInput, (error, stdout, stderr) => {
        if (error) {
            console.error(`exec error: \${error}`);
            return;
        }
        console.log(`stdout: \${stdout}`);
    });
}

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

How to fix Improper Neutralization of Expression/Command Delimiters?

To secure the code, avoid using exec with concatenated strings that include user input. Instead, use execFile or spawn from the child_process module with an array of arguments. These methods do not invoke a shell, preventing command injection vulnerabilities by treating each argument as a separate entity.

Fixed Code Example

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

function executeCommand(userInput) {
    // Fix: Use spawn with an array of arguments to safely handle user input
    // This method does not invoke a shell, thus preventing command injection
    const child = spawn('echo', [userInput]);

    child.stdout.on('data', (data) => {
        console.log(`stdout: \${data}`);
    });

    child.stderr.on('data', (data) => {
        console.error(`stderr: \${data}`);
    });

    child.on('error', (error) => {
        console.error(`error: \${error}`);
    });
}

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

These examples demonstrate how improper handling of command delimiters can lead to vulnerabilities, and how using language-specific safe execution functions can effectively mitigate these risks. By using spawn with an array of arguments, each input is treated as a separate entity, reducing the risk of command injection attacks.