Cloudflare Discloses Technical Details Behind Massive Outage that Breaks the Internet

Overview

On November 18, 2025, Cloudflare experienced a global outage affecting a significant portion of internet services. The outage was caused by a configuration change to a ClickHouse database cluster, which caused a Bot Management feature file to grow beyond expected limits. This triggered a software crash across Cloudflare’s network, resulting in widespread unavailability of websites and services relying on Cloudflare. The outage was not the result of a cyberattack, but rather a latent bug in Cloudflare’s systems exposed by the change.

Who It Impacts

• Organizations using Cloudflare CDN, DNS, and security services (e.g., WAF, Bot Management).
• Users of web platforms dependent on Cloudflare infrastructure, including high-traffic sites like ChatGPT, X, Canva, and other global services.
• IT and security teams responsible for uptime and incident response within affected organizations.

How It Impacts

• Interruption of access to websites and APIs relying on Cloudflare services.
• Failures in Cloudflare-dependent security services, including Bot Management, Workers KV, and Turnstile (CAPTCHA).
• Operational disruption due to cascading software failures across nodes with inconsistent feature file versions.
• Increased risk of misinterpreting the outage as a cyberattack, potentially leading to unnecessary security escalation.

Targeted Products

• Cloudflare CDN – Content delivery interruptions.
• Cloudflare DNS – Potential domain resolution issues.
• Cloudflare Bot Management – Feature file crash affecting bot detection.
• Cloudflare Workers & KV – Edge computing and storage impacted.
• Turnstile / CAPTCHA – Authentication flows disrupted.

Recommendations

1. Review Dependencies
   • Identify critical systems relying on Cloudflare services.
   • Assess the business continuity impact of Cloudflare outages.
2. Enhance Redundancy
   • Consider multi-CDN or multi-DNS strategies to avoid single points of failure.
   • Evaluate backup options for authentication or edge services.
3. Strengthen Change Control & Monitoring
   • Apply strict change management and staged rollouts.
   • Monitor for proxy/edge errors (HTTP 5xx) as well as origin errors.
4. Coordinate with Cloudflare
   • Request post-mortem and mitigation plans from Cloudflare.
   • Confirm SLAs and safeguards for configuration changes and file propagation.
5. Update Incident Response Plans
   • Include scenarios where third-party services cause outages.
   • Run disaster recovery drills simulating CDN/DNS provider failures.
6. Communication Planning
   • Prepare internal and external communications for vendor-induced outages.
   • Clearly inform stakeholders of the outage cause and mitigation steps.
7. Strategic Risk Review
   • Reassess third-party infrastructure dependency in risk registers.
   • Evaluate cost vs risk for diversifying internet infrastructure vendors.

References

https://www.ghacks.net/2025/11/19/cloudflare-says-the-outage-on-tuesday-was-due-to-a-bug-in-its-bot…

https://cybersecuritynews.com/cloudflare-massive-outage-details