Post Mortem

What came first: the CNAME or the A record?

2026-01-14

A recent change to 1.1.1.1 accidentally altered the order of CNAME records in DNS responses, breaking resolution for some clients. This post explores the technical root cause, examines the source code of affected resolvers, and dives into the inherent ambiguities of the DNS RFCs. ...

Cloudflare outage on December 5, 2025

2025-12-05

Cloudflare experienced a significant traffic outage on December 5, 2025, starting approximately at 8:47 UTC. The incident lasted approximately 25 minutes before resolution. We are sorry for the impact that it caused to our customers and the Internet. The incident was not caused by an attack and was due to configuration changes being applied to attempt to mitigate a recent industry-wide vulnerability impacting React Server Components....