On November 18, 2025, Cloudflare experienced a significant outage that disrupted numerous online services, including ChatGPT, X, and Downdetector. The company referred to this incident as the "worst since 2019" and attributed it to a fault in the bot management system.
The issue originated from an incorrect configuration of a request in the ClickHouse database, which generates the configuration file for machine learning models used in bot management. Changes in request behavior resulted in a large number of data duplicates, leading to a rapid increase in the configuration file size that exceeded memory limits.
As a consequence, the primary proxy system that manages client traffic reliant on the bot module failed. Clients utilizing the generated bot metrics in their rules began blocking legitimate traffic, while those who did not implement this feature remained online.
Cloudflare clarified that the problem was not related to DNS, attacks, or new generative AI systems; the error was specifically in the internal logic of updating the bot management configuration.

To prevent similar incidents in the future, the company has announced four measures:

• enhancing the handling of configuration files as well as user input;
• expanding the number of global "kill switches" for features;
• preventing situations where core dumps or error reports may overload the system;
• reviewing all failover modes in critical proxy modules.

According to Cloudflare, approximately 20% of the internet passes through its network, so any error in core modules can have a global impact.