Subdomain Takeover on Aws
How Subdomain Takeover Manifests in Aws
Subdomain takeover in Aws environments typically occurs when a DNS record points to an Aws service that has been deleted or decommissioned, leaving the subdomain vulnerable to external control. This vulnerability is particularly prevalent in Aws due to the platform's ephemeral nature and the ease with which services can be spun up and down.
The most common manifestation involves CloudFront distributions. When a CloudFront distribution is deleted but the DNS CNAME record remains pointing to the distribution's domain (e.g., d111111abcdef8.cloudfront.net), an attacker can create a new CloudFront distribution with the same domain name and serve malicious content from the legitimate subdomain.
Aws-Specific Detection
Detecting subdomain takeover in Aws requires a combination of DNS enumeration and service availability checks. The process begins with identifying all DNS records pointing to Aws services, then verifying whether those services still exist.
For CloudFront detection, the key is checking if the distribution domain resolves to an active CloudFront endpoint. If the DNS resolves but the distribution ID doesn't exist in the account, this indicates a potential takeover.
Aws-Specific Remediation
Remediating subdomain takeover in Aws environments requires both immediate mitigation and long-term prevention strategies. The first step is always removing or updating the vulnerable DNS records.
For CloudFront, if you discover a stale CNAME record, update your DNS provider to remove the CNAME or point it to a valid distribution. Aws Route53 provides programmatic DNS management that can be integrated into your deployment pipelines.