Understanding Critical Information Disclosure Vulnerability via CNAME

Introduction

In today’s digital landscape, data security is of utmost importance. However, one commonly overlooked vulnerability is critical information disclosure via CNAME (Canonical Name) records in DNS. CNAME records are widely used in DNS configurations, allowing one domain to act as an alias for another. While they are typically safe, improper use or misconfiguration can lead to data leaks, leaving sensitive information exposed to malicious actors.

In this blog, we will explore what CNAME records are, how they can lead to critical information disclosure, real-world examples, and best practices to mitigate the risks. By understanding these details, organizations can take proactive measures to prevent this type of vulnerability.

1. What is a CNAME Record?

CNAME is short for Canonical Name. It’s a type of DNS (Domain Name System) record that maps an alias name to a true or canonical domain name. For example, if www.example.com has a CNAME record pointing to example.com, then visiting www.example.com will actually bring the user to example.com.

CNAME records are useful for:

• Redirecting multiple domains to a single server or IP.
• Making domain name…