What came first: the CNAME or the A record?

On January 8, 2026, a change in Cloudflare’s 1.1.1.1 resolver that reordered CNAME records to save memory inadvertently caused widespread DNS resolution failures for clients that assumed CNAMEs appear first (notably glibc’s getaddrinfo and some Cisco switches). The rollout began on January 7, the incident was declared on January 8, and the change was rapidly reverted to restore normal operation. The root cause stems from decades-old ambiguity in DNS RFCs regarding record ordering; Cloudflare reverted the behavior, added safeguards, and authored an Internet-Draft to clarify correct handling of CNAMEs across the ecosystem.