Cloudflare 1.1.1.1 incident on June 27, 2024

On June 27, 2024, Cloudflare experienced an incident with its 1.1.1.1 DNS resolver service due to a combination of BGP hijacking and a route leak. The root cause was identified as a mix of BGP hijacking and a route leak, impacting users globally. Despite efforts like RPKI adoption, the incident caused unreachability for the DNS resolver address from over 300 networks in 70 countries, affecting less than 1% of users in some countries. Cloudflare took steps to address the issue, including disabling peering locations and engaging with relevant network operators. The incident timeline detailed the actions taken to resolve the impact, which included disabling peering points and engaging with AS267613 and AS262504. The impact varied, with some users unable to reach 1.1.1.1 at all, while others experienced high latency per request. Cloudflare's response involved technical analysis using tools like public route collectors and the monocle tool to investigate the rogue BGP updates. The incident highlighted the challenges posed by BGP hijacks and route leaks, emphasizing the importance of continued vigilance and improvement in detecting and mitigating such incidents.