What is Reliance on IP Address for Authentication (CWE-291)?

TL;DR: Reliance on IP Address for Authentication (CWE-291) occurs when a product uses an IP address for authentication, allowing malicious users to fake authentication information and impersonate any IP address.

At-a-Glance Table

What is Reliance on IP Address for Authentication?

Reliance on IP Address for Authentication (CWE-291) is a type of authentication vulnerability that occurs when a product uses an IP address for authentication. As defined by the MITRE Corporation under CWE-291, and classified by the OWASP Foundation under A07:2025 - Authentication Failures, this vulnerability allows malicious users to fake authentication information and impersonate any IP address.

Quick Summary

Reliance on IP Address for Authentication (CWE-291) is a critical vulnerability that occurs when a product uses an IP address for authentication. This vulnerability allows malicious users to fake authentication information and impersonate any IP address, compromising access control and non-repudiation. To fix this vulnerability, use other means of identity verification that cannot be simply spoofed, such as username/password or certificates, and implement proper authentication mechanisms.

Jump to: What is Reliance on IP Address for Authentication? · Quick Summary · Reliance on IP Address for Authentication Overview · How Reliance on IP Address for Authentication Works · Business Impact of Reliance on IP Address for Authentication · Reliance on IP Address for Authentication Attack Scenario · How to Detect Reliance on IP Address for Authentication · How to Fix Reliance on IP Address for Authentication · Framework-Specific Fixes for Reliance on IP Address for Authentication · How to Ask AI to Check Your Code for Reliance on IP Address for Authentication · Reliance on IP Address for Authentication Best Practices Checklist · Reliance on IP Address for Authentication FAQ · Vulnerabilities Related to Reliance on IP Address for Authentication · References · Scan Your Own Site

Reliance on IP Address for Authentication Overview

What: Reliance on IP Address for Authentication (CWE-291) is a type of authentication vulnerability that occurs when a product uses an IP address for authentication.

Why it matters: This vulnerability allows malicious users to fake authentication information and impersonate any IP address, compromising access control and non-repudiation.

Where it occurs: Reliance on IP Address for Authentication (CWE-291) can occur in web applications, network protocols, and other systems that use IP addresses for authentication.

Who is affected: Any user or system that uses a product with this vulnerability is affected.

Who is NOT affected: Systems that do not use IP addresses for authentication are not affected by Reliance on IP Address for Authentication (CWE-291).

How Reliance on IP Address for Authentication Works

Root Cause

Reliance on IP Address for Authentication (CWE-291) occurs when a product uses an IP address for authentication.

Attack Flow

1. The attacker sends a request to the server with a fake IP address.
2. The server authenticates the request using the IP address as the username.
3. The attacker gains access to the system, compromising access control and non-repudiation.

Prerequisites to Exploit

• The product must use an IP address for authentication.
• The attacker must have knowledge of the IP address used by the product.

Vulnerable Code

import requests

def authenticate(ip_address):
    response = requests.get(f'http://example.com/{ip_address}')
    if response.status_code == 200:
        return True
    else:
        return False

This code uses an IP address as the username for authentication, making it vulnerable to Reliance on IP Address for Authentication (CWE-291).

Secure Code

import requests

def authenticate(username, password):
    response = requests.get(f'http://example.com/{username}/{password}')
    if response.status_code == 200:
        return True
    else:
        return False

This code uses a username and password for authentication, making it secure against Reliance on IP Address for Authentication (CWE-291).

Business Impact of Reliance on IP Address for Authentication

Confidentiality: The confidentiality of user data is compromised when an attacker gains access to the system using a fake IP address.

Integrity: The integrity of user data is compromised when an attacker modifies or deletes data using a fake IP address.

Availability: The availability of the system is compromised when an attacker brings down the system by overwhelming it with requests from multiple IP addresses.

Reliance on IP Address for Authentication Attack Scenario

1. The attacker sends a request to the server with a fake IP address.
2. The server authenticates the request using the IP address as the username.
3. The attacker gains access to the system, compromising access control and non-repudiation.

How to Detect Reliance on IP Address for Authentication

Manual Testing

• Review your code for potential vulnerabilities.
• Test your application with different IP addresses to ensure that it can handle multiple authentications correctly.

Automated Scanners (SAST/DAST)

• Use automated scanners to detect potential vulnerabilities in your code.
• These scanners can help identify potential issues before they become major problems.

PenScan Detection

• PenScan’s scanner engines actively test for this issue.
• Our detection capabilities are designed to catch even the most subtle vulnerabilities.

False Positive Guidance

• Be cautious when reviewing false positives, as some may be legitimate issues that need attention.
• Always review your code and configuration carefully before dismissing a finding as a false positive.

How to Fix Reliance on IP Address for Authentication

• Use other means of identity verification that cannot be simply spoofed, such as username/password or certificates.
• Implement proper authentication mechanisms, such as multi-factor authentication.

Framework-Specific Fixes for Reliance on IP Address for Authentication

Java

import java.net.InetAddress;
import java.net.UnknownHostException;

public class Authenticator {
    public boolean authenticate(String ip_address) {
        try {
            InetAddress address = InetAddress.getByName(ip_address);
            return true;
        } catch (UnknownHostException e) {
            return false;
        }
    }
}

Node.js

const net = require('net');

function authenticate(ip_address) {
    const client = new net.Socket();
    client.connect(80, ip_address, () => {
        console.log('Connected to server');
    });
    client.on('error', (err) => {
        console.error('Error connecting to server:', err);
    });
}

Python/Django

import requests

def authenticate(ip_address):
    response = requests.get(f'http://example.com/{ip_address}')
    if response.status_code == 200:
        return True
    else:
        return False

How to Ask AI to Check Your Code for Reliance on IP Address for Authentication

You can ask an AI coding assistant to review your code and suggest improvements. Here is a copy-pasteable prompt you can use:

Review the following Python code block for potential CWE-291 Reliance on IP Address for Authentication vulnerabilities and rewrite it using proper authentication mechanisms:

import requests

def authenticate(ip_address):
    response = requests.get(f'http://example.com/{ip_address}')
    if response.status_code == 200:
        return True
    else:
        return False

Reliance on IP Address for Authentication Best Practices Checklist

✅ Use other means of identity verification that cannot be simply spoofed, such as username/password or certificates. ✅ Implement proper authentication mechanisms, such as multi-factor authentication. ✅ Review your code regularly to ensure it is secure and up-to-date.

Reliance on IP Address for Authentication FAQ

How does Reliance on IP Address for Authentication occur?

Reliance on IP Address for Authentication occurs when a product uses an IP address for authentication, allowing malicious users to fake authentication information and impersonate any IP address.

What are the common consequences of Reliance on IP Address for Authentication?

The common consequences of Reliance on IP Address for Authentication include hiding activities, gaining privileges or assuming identity, and compromising access control and non-repudiation.

How can I detect Reliance on IP Address for Authentication in my application?

You can detect Reliance on IP Address for Authentication by using manual testing, automated scanners (SAST/DAST), PenScan detection, and reviewing your code for potential vulnerabilities.

What are the best practices to prevent Reliance on IP Address for Authentication?

The best practices to prevent Reliance on IP Address for Authentication include using other means of identity verification that cannot be simply spoofed, such as username/password or certificates, and implementing proper authentication mechanisms.

Can AI assist in detecting and preventing Reliance on IP Address for Authentication?

Yes, AI can assist in detecting and preventing Reliance on IP Address for Authentication by reviewing your code for potential vulnerabilities and suggesting improvements to your authentication mechanisms.

What are the related weaknesses to Reliance on IP Address for Authentication?

The related weaknesses to Reliance on IP Address for Authentication include CWE-290 (Authentication Bypass by Spoofing) and CWE-923 (Improper Restriction of Communication Channel to Intended Endpoints).

Vulnerabilities Related to Reliance on IP Address for Authentication

References

• MITRE CWE-291
• OWASP A07:2025 - Authentication Failures
• CAPEC-4
• 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 Reliance on IP Address for Authentication and other risks before an attacker does.