What is Using Referer Field for Authentication (CWE-293)?

TL;DR: CWE-293 Using Referer Field for Authentication is a type of authentication failure vulnerability that occurs when the referer field in HTTP requests can be easily modified. It can lead to actions being carried out as if validated by the server referred to, resulting in gaining privileges or assuming identity.

What is Using Referer Field for Authentication?

Using Referer Field for Authentication (CWE-293) is a type of authentication failure vulnerability that occurs when the referer field in HTTP requests can be easily modified, making it an invalid means of message integrity checking. As defined by the MITRE Corporation under CWE-293, and classified by the OWASP Foundation under A07:2025 - Authentication Failures, this vulnerability can lead to actions being carried out as if validated by the server referred to, resulting in gaining privileges or assuming identity.

Quick Summary

CWE-293 Using Referer Field for Authentication is a critical security vulnerability that occurs when the referer field in HTTP requests can be easily modified. This can lead to actions being carried out as if validated by the server referred to, resulting in gaining privileges or assuming identity. It’s essential to detect and fix this vulnerability to prevent unauthorized access to sensitive data.

Jump to: Quick Summary · Using Referer Field for Authentication Overview · How Using Referer Field for Authentication Works · Business Impact of Using Referer Field for Authentication · Using Referer Field for Authentication Attack Scenario · How to Detect Using Referer Field for Authentication · How to Fix Using Referer Field for Authentication · Framework-Specific Fixes for Using Referer Field for Authentication · How to Ask AI to Check Your Code for Using Referer Field for Authentication · Using Referer Field for Authentication Best Practices Checklist · Using Referer Field for Authentication FAQ · Vulnerabilities Related to Using Referer Field for Authentication · References · Scan Your Own Site

Using Referer Field for Authentication Overview

What: CWE-293 Using Referer Field for Authentication is a type of authentication failure vulnerability that occurs when the referer field in HTTP requests can be easily modified.

Why it matters: This vulnerability can lead to actions being carried out as if validated by the server referred to, resulting in gaining privileges or assuming identity.

Where it occurs: CWE-293 Using Referer Field for Authentication typically occurs in web applications that use the referer field for authentication purposes.

Who is affected: Any user who interacts with a web application that uses the referer field for authentication may be affected by this vulnerability.

Who is NOT affected: Applications that never construct paths/queries/commands from external input are not affected by CWE-293 Using Referer Field for Authentication.

How Using Referer Field for Authentication Works

Root Cause

CWE-293 Using Referer Field for Authentication occurs when the referer field in HTTP requests can be easily modified, making it an invalid means of message integrity checking.

Attack Flow

1. An attacker modifies the referer field in a HTTP request.
2. The web application uses the modified referer field to authenticate the user.
3. The attacker gains access to sensitive data or performs unauthorized actions.

Prerequisites to Exploit

• The web application must use the referer field for authentication purposes.
• The attacker must be able to modify the referer field in a HTTP request.

Vulnerable Code

import requests

def get_referer():
    referer = request.headers.get('Referer')
    if referer:
        return referer
    else:
        return None

This code demonstrates how CWE-293 Using Referer Field for Authentication can occur. The get_referer() function retrieves the referer field from the HTTP request headers and returns it.

Secure Code

import requests

def get_referer():
    referer = request.headers.get('Referer')
    if referer:
        # Verify the referer field using a secure method (e.g. cryptographic hash)
        verified_refferer = verify_referer(referer)
        return verified_refferer
    else:
        return None

This code demonstrates how CWE-293 Using Referer Field for Authentication can be fixed. The get_referer() function retrieves the referer field from the HTTP request headers and verifies it using a secure method (e.g. cryptographic hash).

Business Impact of Using Referer Field for Authentication

Confidentiality: CWE-293 Using Referer Field for Authentication can lead to actions being carried out as if validated by the server referred to, resulting in gaining privileges or assuming identity.

• Integrity: CWE-293 Using Referer Field for Authentication can also lead to unauthorized modifications of sensitive data.
• Availability: CWE-293 Using Referer Field for Authentication can disrupt the availability of web applications and services.

Real-world business consequences:

• Financial losses due to unauthorized access or modifications of sensitive data.
• Compliance issues due to failure to protect sensitive data.
• Reputation damage due to public disclosure of security vulnerabilities.

Using Referer Field for Authentication Attack Scenario

1. An attacker modifies the referer field in a HTTP request.
2. The web application uses the modified referer field to authenticate the user.
3. The attacker gains access to sensitive data or performs unauthorized actions.

How to Detect Using Referer Field for Authentication

Manual Testing

• Use tools like Burp Suite or ZAP to modify the referer field in a HTTP request.
• Observe how the web application responds to the modified referer field.
• Verify that the web application uses a secure method (e.g. cryptographic hash) to verify the referer field.

Automated Scanners (SAST/DAST)

Automated scanners can detect CWE-293 Using Referer Field for Authentication by analyzing the web application’s code and identifying potential vulnerabilities.

• Static Analysis: Automated scanners can analyze the web application’s code and identify potential vulnerabilities.
• Dynamic Analysis: Automated scanners can simulate HTTP requests and observe how the web application responds to potential vulnerabilities.

PenScan Detection

PenScan’s scanner engines actively test for CWE-293 Using Referer Field for Authentication by analyzing the web application’s code and identifying potential vulnerabilities.

False Positive Guidance

To avoid false positives, ensure that the referer field is properly configured and verified using a secure method (e.g. cryptographic hash).

How to Fix Using Referer Field for Authentication

• Use strong authentication and method protection.
• Reject direct user control of configuration.
• Enforce authorization/least-privilege before any configuration change.

Framework-Specific Fixes for Using Referer Field for Authentication

Python/Django

import requests

def get_referer():
    referer = request.headers.get('Referer')
    if referer:
        # Verify the referer field using a secure method (e.g. cryptographic hash)
        verified_refferer = verify_referer(referer)
        return verified_refferer
    else:
        return None

Java/Node.js

import java.util.HashMap;
import java.util.Map;

public class RefererVerifier {
    public static String getReferer(Map<String, String> headers) {
        String referer = headers.get("Referer");
        if (referer != null) {
            // Verify the referer field using a secure method (e.g. cryptographic hash)
            verified_refferer = verify_referer(referer);
            return verified_refferer;
        } else {
            return null;
        }
    }
}

PHP

function getReferer() {
    $referer = $_SERVER['HTTP_REFERER'];
    if ($referer) {
        // Verify the referer field using a secure method (e.g. cryptographic hash)
        verified_refferer = verify_referer($referer);
        return verified_refferer;
    } else {
        return null;
    }
}

How to Ask AI to Check Your Code for Using Referer Field for Authentication

Review the following Python code block for potential CWE-293 Using Referer Field for Authentication vulnerabilities and rewrite it using strong authentication and method protection: [paste code here]

Using Referer Field for Authentication Best Practices Checklist

✅ Use strong authentication and method protection. ✅ Reject direct user control of configuration. ✅ Enforce authorization/least-privilege before any configuration change.

Using Referer Field for Authentication FAQ

How do I define CWE-293 Using Referer Field for Authentication?

CWE-293 Using Referer Field for Authentication is a type of authentication failure vulnerability that occurs when the referer field in HTTP requests can be easily modified, making it an invalid means of message integrity checking.

What are the common consequences of CWE-293 Using Referer Field for Authentication?

The common consequences of CWE-293 Using Referer Field for Authentication include gaining privileges or assuming identity due to actions being carried out as if validated by the server referred to.

How do I detect CWE-293 Using Referer Field for Authentication in my application?

You can detect CWE-293 Using Referer Field for Authentication through manual testing, automated scanners (SAST/DAST), and PenScan detection.

What are some best practices to prevent CWE-293 Using Referer Field for Authentication?

Some best practices include using strong authentication and method protection, rejecting direct user control of configuration, and enforcing authorization/least-privilege before any configuration change.

Can you provide an example of vulnerable code for CWE-293 Using Referer Field for Authentication?

Yes, the following is an example of vulnerable code in Python:

How do I fix CWE-293 Using Referer Field for Authentication in my application?

You can fix CWE-293 Using Referer Field for Authentication by using strong authentication and method protection, rejecting direct user control of configuration, and enforcing authorization/least-privilege before any configuration change.

What are some framework-specific fixes for CWE-293 Using Referer Field for Authentication?

Some framework-specific fixes include using the @RolesAllowed annotation in EJB, implementing the SecureZeroMemory() function in C++, or using the SECURE_SSL_REDIRECT = True setting in Django.

Can you provide an example of how to ask AI to check your code for CWE-293 Using Referer Field for Authentication?

Yes, you can use the following prompt with an AI coding assistant: Review the following Python code block for potential CWE-293 Using Referer Field for Authentication vulnerabilities and rewrite it using strong authentication and method protection: [paste code here]

Vulnerabilities Related to Using Referer Field for Authentication

References

• MITRE CWE-293
• OWASP A07:2025 - Authentication Failures
• 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 Using Referer Field for Authentication and other risks before an attacker does.