On November 18th, Cloudflare, one of the largest content delivery and security networks in the world, experienced a major outage that disrupted a significant portion of the internet. Initially, Cloudflare’s team suspected a massive distributed denial-of-service attack, but after investigation, the issue was traced to a corrupt configuration file within its internal systems.
The problem stemmed from a change made to Cloudflare’s internal systems, which caused a critical configuration file used by their bot management system to unexpectedly double in size. This malformed file was rapidly propagated across Cloudflare’s network, overwhelming its servers and causing widespread failures. The outage led to accessibility issues for major websites and online services, including social media platforms like X (Twitter) and ChatGPT, which were rendered temporarily unavailable for millions of users.
What is Cloudflare?
Cloudflare is a global internet infrastructure company that provides performance, security, and reliability services for websites. Acting as a content delivery network (CDN) and reverse proxy, Cloudflare caches content across its global network to speed up site load times and ensure users connect to the fastest server.
Cloudflare’s core function is to protect websites from online threats by acting like a middle man for all the traffic. It defends against DDoS attacks, malicious bots, and spammers by filtering traffic before it reaches the website’s server. Using a combination of firewall rules, rate-limiting, and machine learning, it blocks harmful traffic while allowing legitimate users through. Cloudflare also provides SSL/TLS encryption for secure data transmission and DNS management for reliable site performance. In short, Cloudflare acts as a security barrier and performance enhancer, keeping websites safe and fast.
The Outage
The outage began when Cloudflare's core services started failing across its global network, causing hundreds of websites to go offline or become inaccessible. Users reported being hit with HTTP 500 errors—a sign that Cloudflare’s servers were unable to process requests properly. Sites like X and ChatGPT were among the largest affected, as they depend on Cloudflare’s security and performance infrastructure. Millions of other websites relying on cloudflare were also impacted, including our website which became unaveilable during the outage.
Initially, Cloudflare’s team suspected a massive DDoS attack as the cause of the disruption, given the sudden and widespread nature of the failures. The unusual surge in traffic seemed to match the pattern of an attack, and the company’s initial focus was on mitigating external threats. However, as the issue persisted, Cloudflare realized the problem was internal.
What Caused the Outage?
The root cause of the outage was traced to a corrupt configuration file used by Cloudflare’s bot management system, which unexpectedly doubled in size due to a system misconfiguration. This file, essential for filtering out malicious bots and managing traffic flow, became malformed when additional, unexpected metadata was included. As the corrupted file was propagated across Cloudflare’s global network, it overwhelmed the infrastructure, preventing the servers from properly handling incoming traffic and causing widespread failures.
Once the team identified the faulty file, they replaced it with a correct version and halted its propagation. While most services were quickly restored, the surge in traffic from users rushing back online added additional strain, and it took several more hours to fully stabilize the system. The outage, which became Cloudflare’s worst since 2019, revealed critical vulnerabilities in their error handling and failover systems, prompting a review and overhaul of their internal processes to prevent similar issues in the future.
Conclusion
The November 2025 Cloudflare outage highlighted the risks of relying on a single provider for such a vast portion of the internet’s infrastructure. With millions of websites, including major platforms like X and ChatGPT, depending on Cloudflare for security and performance, any disruption can cause widespread accessibility issues. This event raises concerns about the centralization of internet services and the potential impact of a single point of failure. While Cloudflare has worked to resolve the issue, it’s a reminder of the need for more robust, distributed systems that can withstand similar failures and ensure the resilience of the digital ecosystem.
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