Cloudflare November 18 Global Outage – Causes, Impact, and How to Stay Protected
Introduction
On November 18, Cloudflare experienced a significant global outage that caused widespread disruption across websites, APIs, applications, and online services. As one of the world’s largest CDN and security providers, any Cloudflare outage has a massive ripple effect across the internet.
This article explains what caused the Cloudflare outage, the global impact, and practical steps organizations can take to reduce downtime in future CDN failures.
On November 18th, Cloudflare, the world's largest CDN and cybersecurity service provider, experienced its most severe outage since 2019. Multiple websites using Cloudflare encountered 5xx errors, causing access disruptions, and even services like authentication, KV storage, and Turnstile were briefly paralyzed.
What Happened During the Cloudflare November 18 Outage?
Cloudflare reported that the outage was triggered by issues within their core network routing layer, affecting:
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DNS resolution
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CDN edge nodes
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Website and API responsiveness
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Application security services
Many users experienced:
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“Connection timed out”
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“Error 500/502”
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“Website not reachable”
π According to the official Cloudflare Status page, the outage impacted multiple regions at the same time, making it one of the year's largest disruptions:
External link: https://www.cloudflarestatus.com/
Timeline of the incident:
11:05 — A database permission change was deployed
11:20–11:28 — 5xx errors began appearing globally, marking the full outbreak of theζ ι
13:05 — KV and Access services underwent emergency bypass procedures, partially restoring service
14:30 — The faulty Bot Management configuration file was replaced, restoring most traffic
17:06 — All systems returned to normal
The entire incident lasted approximately 6 hours
Why did the outage occur? (Official technical explanation)
Cloudflare's Bot Management system generates a "signature file" (used to determine if a visitor is a bot) every few minutes.
This database permission update caused a backend SQL query to return an additional batch of data from "underlying shard tables," unexpectedly doubling the file size.
The maximum number of signatures supported by Cloudflare's proxy software is about 200.
Normally, only around 60 are used.
However, this time the generated file exceeded the expected size due to the doubled content, causing all proxy modules to panic (crash), resulting in widespread 5xx errors globally.
Since most Cloudflare products rely on the proxy module, services like KV, Access, and Turnstile were also affected simultaneously.
How to Protect Your Website from Future CDN Outages
✔ 1. Use Multi-CDN Architecture
Deploying backup CDNs (CloudFront, Fastly, Akamai) can keep websites online even if Cloudflare fails.
✔ 2. Implement Redundant DNS Providers
Combine Cloudflare DNS with:
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Google DNS
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Route53
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Quad9
✔ 3. Enable Local Caching & Failover
Store essential static assets locally or use browser-level caching to reduce impact.
✔ 4. Monitor Availability 24/7
Tools like:
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UptimeRobot
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BetterStack
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Pingdom
help track outages in real time.
✔ 5. Prepare an Incident Response Plan
Have a documented plan for:
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Switching DNS records
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Communicating with customers
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Using failover IP routing
π Best practice reference:
External Source: https://www.cloudflare.com/learning/cdn/what-is-a-cdn/
Conclusion
The Cloudflare November 18 global outage shows how dependent the modern internet is on centralized infrastructure. While incidents like this are rare, businesses can dramatically reduce risks by implementing redundant CDNs, multi-DNS, caching, and monitoring systems.
By learning from this event, organizations can build more resilient, outage-proof architectures for the future.
Related Reading: An Alternative Method to Defend Against Ransomware – Advanced Data Protection Strategies