The Day the Internet Stalled: Cloudflare's Massive Global Outage Explained

11/20/20252 min read

The Widespread Fallout

Cloudflare sits at a critical junction of the internet, providing services like Content Delivery Networks (CDN), DDoS protection, and security firewalls. When its core systems fail, the impact ripples across the web.

The outage, which began around 11:20 UTC and lasted for several hours, caused major disruptions for an array of global services, including:

  • X (formerly Twitter)

  • OpenAI's ChatGPT

  • Spotify

  • Canva

  • League of Legends

  • Even the outage-tracking website Downdetector was reportedly hit.

For many users, the error messages indicated a problem with the Cloudflare layer itself, highlighting just how dependent modern digital life is on a handful of central providers.

The Root Cause: A Latent Bug and an Oversized File

In their post-incident report, Cloudflare's CEO and CTO clarified that the massive disruption was not a breach or attack, but a bug that went latent—or undetected—until specific conditions triggered it.

The chain of events was as follows:

  1. A Routine Change: The incident was initiated by a routine change to the permissions within one of Cloudflare's internal database systems.

  2. The Bug is Triggered: This change exposed a latent bug in the logic that generates a configuration file for their Bot Management system, which is designed to identify and block threat traffic.

  3. Oversized Configuration: The faulty generation logic caused the configuration file to contain a large number of duplicate entries, effectively doubling its file size beyond expected limits.

  4. The System Crashes: When this now-oversized file was distributed across Cloudflare's global network, the software in the core proxy system attempted to load it. The file size exceeded the software's hard limits, causing the core system responsible for routing and processing customer traffic to crash repeatedly.

The Fluctuation and Recovery

A key challenge during the incident was the unusual failure pattern. Because the faulty configuration file was being regenerated every five minutes on a partially updated database cluster, the system experienced an intermittent cycle of failure and recovery.

This fluctuation initially led Cloudflare engineers to suspect a sophisticated, hyper-scale Distributed Denial of Service (DDoS) attack, delaying the correct diagnosis. Once the internal database issue was identified, the team stopped the generation of the bad file and manually inserted a known-good configuration.

Cloudflare officially declared the incident resolved later that afternoon, apologizing to its customers and "the internet in general for letting you down today," and committing to hardening their systems to prevent a recurrence.

The outage serves as a stark reminder of the single points of failure in the modern internet ecosystem, where even a small error in one crucial layer can bring down global services for millions of users.