CWE-142: Improper Neutralization of Value Delimiters

What is Improper Neutralization of Value Delimiters?

• Overview:

• CWE-142, Improper Neutralization of Value Delimiters, occurs when a software application receives input containing special characters that are not properly neutralized, leading to incorrect interpretation as delimiters. This can cause the application to behave unexpectedly when processing data.

• Exploitation Methods:

• Attackers can exploit this vulnerability by injecting special characters into input fields, tricking the system into treating them as delimiters.
• Common attack patterns include manipulating data formats, injecting separators into structured data, or altering configuration files to disrupt processing logic.

• Security Impact:

• Direct consequences of successful exploitation include data corruption, unexpected application behavior, and potential data leakage.
• Potential cascading effects include the breakdown of data integrity and application logic, leading to system instability or crashes.
• Business impact may involve loss of customer trust, regulatory non-compliance, and financial losses due to compromised data.

• Prevention Guidelines:

• Specific code-level fixes involve validating and sanitizing all input data, ensuring special characters are properly handled.
• Security best practices include implementing robust input validation, using whitelists for allowed characters, and escaping or encoding delimiters appropriately.
• Recommended tools and frameworks for prevention include input validation libraries and static analysis tools that can identify improper handling of delimiters in code.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

const express = require('express');
const app = express();

app.get('/search', (req, res) => {
    const searchTerm = req.query.term;
    // Vulnerable to command injection due to improper neutralization of shell arguments
    const command = `grep "\${searchTerm}" data.txt`;
    require('child_process').exec(command, (error, stdout, stderr) => {
        if (error) {
            return res.status(500).send(error.message);
        }
        res.send(stdout);
    });
});

Explanation:

• The above code is vulnerable because it directly interpolates searchTerm into a shell command without proper neutralization. If searchTerm contains special shell characters like ;, it could lead to command injection, allowing an attacker to execute arbitrary commands on the server.

How to fix Improper Neutralization of Value Delimiters?

To fix this vulnerability, use a library that properly escapes shell arguments, such as child_process.execFile, which separates command arguments from the executable in a safe manner.

Fixed Code Example

const express = require('express');
const app = express();

app.get('/search', (req, res) => {
    const searchTerm = req.query.term;
    // Use execFile to safely pass arguments without risk of injection
    require('child_process').execFile('grep', [searchTerm, 'data.txt'], (error, stdout, stderr) => {
        if (error) {
            return res.status(500).send(error.message);
        }
        res.send(stdout);
    });
});

Explanation:

• By using execFile instead of exec, the code separates the command and its arguments, ensuring that searchTerm is not interpreted as part of the command itself.
• This approach prevents command injection by treating searchTerm as a separate argument, neutralizing any special characters that might otherwise be used for injection.
• This method is safer and aligns with best practices for executing shell commands in a Node.js environment.