Subdomain takeover remains a critical yet often overlooked cloud security issue. When a CNAME record points to a deprovisioned external service, attackers can claim that service and gain control of the subdomain. This can lead to phishing, cookie theft, or bypassing security policies. The attack requires no sophisticated tools—just a dangling DNS record and a registration on the target service. Detection involves auditing DNS records against active resources and monitoring for orphaned entries. Prevention includes strict deprovisioning processes, using CNAME validation, and regular DNS hygiene checks. For security engineers, integrating this check into CI/CD pipelines and vulnerability scanners is essential. This article explores the attack chain, real-world impact, and actionable mitigation strategies for teams managing cloud infrastructure.
Learn how dangling CNAME records enable subdomain takeover and how to detect and prevent this cloud security risk.