Cloudflare’s November Outage Halts Major Websites Worldwide, Reveals Internet Vulnerability

Cloudflare, a major provider of internet infrastructure and security services, experienced its worst outage since 2019 on November 18, 2025, causing about 20 percent of the internet, including major websites like X (formerly Twitter), ChatGPT, and Canva, to go offline for nearly five hours. Cloudflare’s Co-Founder and CEO Matthew Prince clarified in a detailed blog post that the outage was caused by an internal system error rather than a cyberattack or malicious activity, drawing widespread attention to the vulnerability of online services.

The root cause was a permissions change in one of Cloudflare’s database systems that generated an abnormally large “feature file” used by the company’s Bot Management system. This oversized file exceeded software limits and was intermittently propagated across Cloudflare's network due to partial updates on database clusters. These fluctuations caused proxy software to fail repeatedly, triggering HTTP 500 internal server errors seen by users. Initial diagnostics mistakenly suspected a large-scale Distributed Denial of Service (DDoS) attack.

Cloudflare’s engineering teams quickly contained the problem by halting the spread of the faulty file, rolling back to a stable version, and restarting critical proxy services. Core traffic returned to normal by 14:30 UTC (8:00 PM IST), with full recovery completed by 17:06 UTC (10:36 PM IST). Key services affected included Cloudflare’s content delivery network (CDN), security systems, Turnstile bot-challenge service, Workers KV key-value store, Access authentication, and email security features, all experiencing elevated error rates or downtime during the incident.

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The outage revealed the complexity and scale of Cloudflare’s infrastructure, which routes and secures a significant percentage of global internet traffic. Prince emphasized the company’s commitment to learning from this incident by enhancing system resilience including hardening configuration file ingestion and enabling global kill switches to prevent future failures. “An outage like today is unacceptable,” he stated, underscoring Cloudflare’s ongoing efforts to build more robust systems capable of withstanding unexpected internal failures.

This event highlighted the interconnectedness of critical web infrastructure and how internal errors at a single provider can ripple across the internet, affecting millions of users and countless services globally. Cloudflare’s transparency and swift remediation were widely regarded as crucial to restoring trust and minimizing prolonged disruption.

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