Atomic

This is a security enforcement feature within the Cloudflare platform. It is designed for Cloudflare administrators and domain owners to maintain control over their DNS configurations and prevent security risks. The system automatically detects and blocks specific CNAME record configurations that violate platform security policies.

• Cross-Account CNAME Blocking: The core function is to prevent CNAME flattening or pointing across different Cloudflare user accounts. This stops one user from improperly associating a domain or subdomain with resources in another user's account without authorization.
• Enforces Domain Ownership: It protects against domain hijacking and misconfiguration by ensuring that only the verified owner of a domain within an account can create DNS records that resolve to their resources.
• Maintains Account Isolation: The feature upholds security boundaries between customer accounts on the shared Cloudflare network. This is a fundamental security measure to prevent accidental or malicious cross-account access.
• Automatic Policy Enforcement: The blocking is applied automatically by Cloudflare's systems when a disallowed CNAME configuration is detected, returning a specific error to the requester. This removes the need for manual review of every DNS change.
• Guides Correct Setup: For services like R2 custom domains, the error message typically directs users to the proper method for configuring custom domains, ensuring they use the supported, secure workflow instead of a manual CNAME workaround.