What is Improper Neutralization of Multiple (CWE-165)?

TL;DR: Improper Neutralization of Multiple Internal Special Elements (CWE-165) occurs when a product receives input from an upstream component but fails to neutralize or incorrectly neutralizes multiple internal special elements that could be interpreted in unexpected ways. To prevent CWE-165, use a combination of denylists and allowlists to ensure only valid input is processed by the system.

At-a-Glance

What is Improper Neutralization of Multiple Internal Special Elements?

Improper Neutralization of Multiple Internal Special Elements (CWE-165) is a type of security vulnerability that occurs when a product receives input from an upstream component but fails to neutralize or incorrectly neutralizes multiple internal special elements that could be interpreted in unexpected ways. As defined by the MITRE Corporation under CWE-165, and classified by the OWASP Foundation under None…

Quick Summary

Improper Neutralization of Multiple Internal Special Elements (CWE-165) is a security vulnerability that can lead to serious consequences if not properly addressed. It occurs when a product receives input from an upstream component but fails to neutralize or incorrectly neutralizes multiple internal special elements that could be interpreted in unexpected ways.

Jump to: Quick Summary · Improper Neutralization of Multiple Internal Special Elements Overview · How Improper Neutralization of Multiple Internal Special Elements Works · Business Impact of Improper Neutralization of Multiple Internal Special Elements · Improper Neutralization of Multiple Internal Special Elements Attack Scenario · How to Detect Improper Neutralization of Multiple Internal Special Elements · How to Fix Improper Neutralization of Multiple Internal Special Elements · Framework-Specific Fixes for Improper Neutralization of Multiple Internal Special Elements · How to Ask AI to Check Your Code for Improper Neutralization of Multiple Internal Special Elements · Improper Neutralization of Multiple Internal Special Elements Best Practices Checklist · Improper Neutralization of Multiple Internal Special Elements FAQ · Vulnerabilities Related to Improper Neutralization of Multiple Internal Special Elements · References · Scan Your Own Site

Improper Neutralization of Multiple Internal Special Elements Overview

Improper Neutralization of Multiple Internal Special Elements (CWE-165) is a security vulnerability that occurs when a product receives input from an upstream component but fails to neutralize or incorrectly neutralizes multiple internal special elements that could be interpreted in unexpected ways.

• What: Improper Neutralization of Multiple Internal Special Elements (CWE-165) occurs when a product receives input from an upstream component but fails to neutralize or incorrectly neutralizes multiple internal special elements that could be interpreted in unexpected ways.
• Why it matters: CWE-165 can lead to security vulnerabilities, data breaches, and system compromise if not properly addressed.
• Where it occurs: CWE-165 typically occurs in web applications, web services, and APIs.
• Who is affected: CWE-165 can affect any organization that uses web applications or APIs.
• Who is NOT affected: Organizations that do not use web applications or APIs are not affected by CWE-165.

How Improper Neutralization of Multiple Internal Special Elements Works

Root Cause

The root cause of CWE-165 is the failure to properly neutralize or validate user input, which can lead to security vulnerabilities and data breaches.

Attack Flow

1. An attacker injects malicious input into a web application or API.
2. The input is not properly validated or sanitized by the product.
3. The product interprets the input in an unexpected way, leading to security vulnerabilities and data breaches.

Prerequisites to Exploit

• The attacker must be able to inject malicious input into the web application or API.
• The product must fail to properly validate or sanitize the user input.

Vulnerable Code

input = request.form['input']
if input.startswith('../'):
    os.chdir(input)

This code is vulnerable because it does not properly validate the user input, which can lead to security vulnerabilities and data breaches.

Secure Code

import os

input = request.form['input']
if not os.path.abspath(input).startswith(base_dir):
    raise ValueError('Invalid input')
else:
    os.chdir(input)

This code is secure because it properly validates the user input before allowing it to be interpreted by the product.

Business Impact of Improper Neutralization of Multiple Internal Special Elements

Improper Neutralization of Multiple Internal Special Elements (CWE-165) can have serious business consequences, including:

• Security vulnerabilities and data breaches
• System compromise and downtime
• Financial losses due to data breaches and system compromise
• Compliance issues due to failure to properly address CWE-165

Improper Neutralization of Multiple Internal Special Elements Attack Scenario

1. An attacker injects malicious input into a web application or API.
2. The product interprets the input in an unexpected way, leading to security vulnerabilities and data breaches.

How to Detect Improper Neutralization of Multiple Internal Special Elements

Manual Testing

• Review code for proper validation and sanitization of user input
• Test product with malicious input to see if it is properly handled

Automated Scanners (SAST / DAST)

• Use automated scanners like PenScan to detect CWE-165
• Contrast what static analysis catches vs. what needs dynamic/runtime testing to find

PenScan Detection

PenScan’s scanner engines actively test for CWE-165 and can help you identify vulnerabilities before an attacker does.

False Positive Guidance

• Be cautious of false positives due to context that a scanner cannot see
• Review findings carefully to ensure they are not false alarms

How to Fix Improper Neutralization of Multiple Internal Special Elements

• Use a combination of denylists and allowlists to ensure only valid input is processed by the system
• Properly validate and sanitize user input before allowing it to be interpreted by the product

Framework-Specific Fixes for Improper Neutralization of Multiple Internal Special Elements

Java

import java.io.File;
import java.io.IOException;

public class CWE165 {
    public static void main(String[] args) throws IOException {
        String input = request.getParameter("input");
        if (!new File(input).isAbsolute()) {
            throw new IllegalArgumentException("Invalid input");
        }
        // ...
    }
}

Node.js

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

app.post('/endpoint', (req, res) => {
    const input = req.body.input;
    if (!input.startsWith('/') && !input.endsWith('/')) {
        throw new Error("Invalid input");
    }
    // ...
});

Python/Django

from django.http import HttpResponse
from django.views.decorators.http import require_http_methods

@require_http_methods(['POST'])
def endpoint(request):
    input = request.POST.get('input')
    if not input.startswith('/') and not input.endswith('/'):
        raise ValueError("Invalid input")
    # ...
    return HttpResponse()

PHP

<?php

function endpoint($request) {
    $input = $request->getPost('input');
    if (!preg_match('#^/.*$#', $input)) {
        throw new Exception("Invalid input");
    }
    // ...
}

?>

How to Ask AI to Check Your Code for Improper Neutralization of Multiple Internal Special Elements

You can ask an AI coding assistant like PenScan’s AI-powered code review tool to check your code for CWE-165 by providing the following prompt:

“Review the following Python code block for potential CWE-165 Improper Neutralization of Multiple Internal Special Elements vulnerabilities and rewrite it using input validation:”

input = request.form['input']
if input.startswith('../'):
    os.chdir(input)

Improper Neutralization of Multiple Internal Special Elements Best Practices Checklist

✅ Use a combination of denylists and allowlists to ensure only valid input is processed by the system. ✅ Properly validate and sanitize user input before allowing it to be interpreted by the product.

Improper Neutralization of Multiple Internal Special Elements FAQ

How do I prevent Improper Neutralization of Multiple Internal Special Elements?

To prevent CWE-165, use a combination of denylists and allowlists to ensure only valid input is processed by the system.

What are some common examples of CWE-165?

CWE-165 can occur when a product receives user input that includes special characters or keywords that could be interpreted in unexpected ways.

How do I detect CWE-165?

Detecting CWE-165 typically involves manual testing and review of code, as well as the use of automated scanners like PenScan.

What are some best practices for preventing CWE-165?

Best practices include using input validation, output encoding, and proper quoting of arguments to prevent special characters from being interpreted in unexpected ways.

Can CWE-165 be exploited remotely?

Yes, CWE-165 can often be exploited remotely if an attacker is able to inject malicious input into a web application or API.

How do I fix CWE-165?

Fixing CWE-165 typically involves updating code to properly validate and sanitize user input, as well as using output encoding and proper quoting of arguments.

Can CWE-165 be prevented through configuration settings alone?

No, preventing CWE-165 typically requires changes to code and may also involve updates to configuration settings.

Vulnerabilities Related to Improper Neutralization of Multiple Internal Special Elements

References

• MITRE CWE-165
• NVD

Scan Your Own Site

Manual code review catches what you know to look for. An automated scan catches what you didn’t. Scan your own website using PenScan to find CWE-165 and other risks before an attacker does.