What is Reliance on Reverse DNS Resolution (CWE-350)?

TL;DR: Reliance on Reverse DNS Resolution for a Security-Critical Action (CWE-350) occurs when an application performs reverse DNS resolution without properly ensuring the IP address is associated with the hostname, leading to potential security breaches.

At-a-Glance Table

What is Reliance on Reverse DNS Resolution for a Security-Critical Action?

Reliance on reverse DNS resolution for a security-critical action is a type of vulnerability that occurs when an application performs reverse DNS resolution to obtain the hostname and make a security decision, but does not properly ensure that the IP address is truly associated with the hostname. As defined by the MITRE Corporation under CWE-350, and classified by the OWASP Foundation under A07:2025 - Authentication Failures, this vulnerability can lead to serious security breaches.

Quick Summary

Reliance on reverse DNS resolution for a security-critical action is a critical vulnerability that occurs when an application performs reverse DNS resolution without properly ensuring the IP address is associated with the hostname. This can lead to gain of privileges or assumption of identity, bypassing protection mechanisms, and malicious users faking authentication information by providing false DNS information.

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

Reliance on Reverse DNS Resolution for a Security-Critical Action Overview

What: Reliance on reverse DNS resolution for a security-critical action occurs when an application performs reverse DNS resolution without properly ensuring the IP address is associated with the hostname.

Why it matters: This vulnerability can lead to serious security breaches, including gain of privileges or assumption of identity, bypassing protection mechanisms, and malicious users faking authentication information by providing false DNS information.

Where it occurs: Reliance on reverse DNS resolution for a security-critical action can occur in any application that performs reverse DNS resolution without proper validation.

Who is affected: Any user who interacts with the vulnerable application may be affected by this vulnerability.

Who is NOT affected: Users who do not interact with the vulnerable application are not affected by this vulnerability.

How Reliance on Reverse DNS Resolution for a Security-Critical Action Works

Root Cause

The root cause of reliance on reverse DNS resolution for a security-critical action is that an application performs reverse DNS resolution without properly ensuring the IP address is associated with the hostname.

Attack Flow

1. The attacker provides false DNS information to the vulnerable application.
2. The vulnerable application performs reverse DNS resolution and relies on the provided DNS information.
3. The attacker gains privileges or assumes identity by exploiting the vulnerability.

Prerequisites to Exploit

• The attacker must provide false DNS information to the vulnerable application.
• The vulnerable application must perform reverse DNS resolution without proper validation.

Vulnerable Code

import socket

def get_hostname(ip_address):
    try:
        hostname = socket.gethostbyaddr(ip_address)[0]
        return hostname
    except Exception as e:
        return None

ip_address = "192.168.1.100"
hostname = get_hostname(ip_address)
if hostname is not None:
    print(f"The hostname for {ip_address} is {hostname}")

The vulnerable code above performs reverse DNS resolution without proper validation, making it susceptible to this vulnerability.

Secure Code

import socket

def get_hostname(ip_address):
    try:
        hostname = socket.gethostbyaddr(ip_address)[0]
        if hostname == ip_address:  # Validate the hostname
            return hostname
        else:
            raise Exception("Hostname does not match IP address")
    except Exception as e:
        return None

ip_address = "192.168.1.100"
hostname = get_hostname(ip_address)
if hostname is not None:
    print(f"The hostname for {ip_address} is {hostname}")

The secure code above performs reverse DNS resolution with proper validation, preventing this vulnerability.

Business Impact of Reliance on Reverse DNS Resolution for a Security-Critical Action

Confidentiality: The confidentiality impact of reliance on reverse DNS resolution for a security-critical action is that sensitive information may be exposed to unauthorized users.

• Impact: Sensitive information may be exposed to unauthorized users.
• Example: An attacker gains access to confidential data by exploiting the vulnerability.

Integrity: The integrity impact of reliance on reverse DNS resolution for a security-critical action is that data may be modified or deleted by unauthorized users.

• Impact: Data may be modified or deleted by unauthorized users.
• Example: An attacker modifies or deletes sensitive data by exploiting the vulnerability.

Availability: The availability impact of reliance on reverse DNS resolution for a security-critical action is that systems or services may become unavailable due to exploitation.

• Impact: Systems or services may become unavailable due to exploitation.
• Example: An attacker exploits the vulnerability, causing a system or service to become unavailable.

Reliance on Reverse DNS Resolution for a Security-Critical Action Attack Scenario

1. The attacker provides false DNS information to the vulnerable application.
2. The vulnerable application performs reverse DNS resolution and relies on the provided DNS information.
3. The attacker gains privileges or assumes identity by exploiting the vulnerability.
4. The attacker modifies or deletes sensitive data by exploiting the vulnerability.

How to Detect Reliance on Reverse DNS Resolution for a Security-Critical Action

Manual Testing

• Check if the application performs reverse DNS resolution without proper validation.
• Verify that the IP address is associated with the hostname.

Automated Scanners (SAST/DAST)

• Use automated scanners to detect potential vulnerabilities in the code.
• Review the scan results to identify potential issues.

PenScan Detection

PenScan’s scanner engines actively test for this issue, providing you with actionable insights to strengthen your security posture.

False Positive Guidance

• Be cautious when reviewing scan results, as false positives may occur.
• Verify the findings by manually testing the application.

How to Fix Reliance on Reverse DNS Resolution for a Security-Critical Action

1. Use other means of identity verification that cannot be simply spoofed, such as usernames and passwords or certificates.
2. Perform proper forward and reverse DNS lookups to detect DNS spoofing.

Framework-Specific Fixes for Reliance on Reverse DNS Resolution for a Security-Critical Action

Java

• Use the java.net.InetAddress class to perform reverse DNS resolution with proper validation.
• Verify that the IP address is associated with the hostname using the getHostByAddr() method.

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

public class ReverseDNSResolution {
    public static void main(String[] args) throws UnknownHostException {
        String ip_address = "192.168.1.100";
        InetAddress inetAddress = InetAddress.getByName(ip_address);
        if (inetAddress.getHostByAddr().equals(ip_address)) {
            System.out.println("The hostname for " + ip_address + " is " + inetAddress.getHostByAddr());
        } else {
            System.out.println("Hostname does not match IP address");
        }
    }
}

Node.js

• Use the dns module to perform reverse DNS resolution with proper validation.
• Verify that the IP address is associated with the hostname using the gethostbyaddr() function.

const dns = require('dns');

function getHostname(ipAddress) {
    dns.gethostbyaddr(ipAddress, (err, hostname) => {
        if (err) {
            console.error(err);
        } else {
            if (hostname === ipAddress) {
                console.log(`The hostname for ${ipAddress} is ${hostname}`);
            } else {
                console.error('Hostname does not match IP address');
            }
        }
    });
}

getHostname("192.168.1.100");

How to Ask AI to Check Your Code for Reliance on Reverse DNS Resolution for a Security-Critical Action

Review the following code block for potential CWE-350 vulnerabilities and rewrite it using primary fix techniques:

import socket

def get_hostname(ip_address):
    try:
        hostname = socket.gethostbyaddr(ip_address)[0]
        return hostname
    except Exception as e:
        return None

ip_address = "192.168.1.100"
hostname = get_hostname(ip_address)
if hostname is not None:
    print(f"The hostname for {ip_address} is {hostname}")

Reliance on Reverse DNS Resolution for a Security-Critical Action Best Practices Checklist

✅ Verify that the IP address is associated with the hostname using proper validation. ✅ Use other means of identity verification that cannot be simply spoofed, such as usernames and passwords or certificates. ✅ Perform proper forward and reverse DNS lookups to detect DNS spoofing.

Reliance on Reverse DNS Resolution for a Security-Critical Action FAQ

How does Reliance on Reverse DNS Resolution for a Security-Critical Action occur?

Reliance on reverse DNS resolution for a security-critical action occurs when an application performs reverse DNS resolution to obtain the hostname and make a security decision, but does not properly ensure that the IP address is truly associated with the hostname.

What are the common consequences of Reliance on Reverse DNS Resolution for a Security-Critical Action?

The common consequences of reliance on reverse DNS resolution for a security-critical action include gain of privileges or assumption of identity, bypassing protection mechanisms, and malicious users faking authentication information by providing false DNS information.

How can I prevent Reliance on Reverse DNS Resolution for a Security-Critical Action?

To prevent reliance on reverse DNS resolution for a security-critical action, use other means of identity verification that cannot be simply spoofed, such as usernames and passwords or certificates. Perform proper forward and reverse DNS lookups to detect DNS spoofing.

Can I use AI to check my code for Reliance on Reverse DNS Resolution for a Security-Critical Action?

Yes, you can use AI to check your code for reliance on reverse DNS resolution for a security-critical action by reviewing the following language code block for potential CWE-350 vulnerabilities and rewriting it using primary fix techniques.

What are some best practices for preventing Reliance on Reverse DNS Resolution for a Security-Critical Action?

Some best practices for preventing reliance on reverse DNS resolution for a security-critical action include verifying return values, testing your code, and using an allowlist to restrict access to sensitive resources.

How can I detect Reliance on Reverse DNS Resolution for a Security-Critical Action in my application?

You can detect reliance on reverse DNS resolution for a security-critical action by performing manual testing, using automated scanners (SAST/DAST), and reviewing your code for potential vulnerabilities.

What are some common framework-specific fixes for Reliance on Reverse DNS Resolution for a Security-Critical Action?

Some common framework-specific fixes for reliance on reverse DNS resolution for a security-critical action include using secure libraries, configuring secure protocols, and implementing authentication mechanisms.

Vulnerabilities Related to Reliance on Reverse DNS Resolution for a Security-Critical Action

References

• MITRE CWE-350
• OWASP A07:2025 - Authentication Failures
• CAPEC-142, CAPEC-275, CAPEC-73, CAPEC-89
• 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 Reverse DNS Resolution for a Security-Critical Action and other risks before an attacker does.