Cloudflare Outage on November 18, 2025 – What Happened
On November 18, 2025 (11:20 UTC), Cloudflare’s network began experiencing
significant failures that prevented traffic from being properly delivered across its infrastructure.
(Source: Cloudflare Blog)
The company confirmed that the cause was not a cyber-attack or malicious activity,
but a mis-configuration in one of their database systems.
This caused one of their “feature files” to grow beyond its expected size and crash modules across
their network.
(Source: Cloudflare Blog)
By 17:06 UTC, all systems were reported to be functioning normally.
What Went Wrong
-
A permissions change in a database system triggered duplicate rows in a key
“feature file” used by Cloudflare’s Bot Management system. -
That feature file doubled in size, exceeding the system’s expectation of a
maximum 200 features, causing modules to fail during distribution. -
Cloudflare’s main proxy system (FL2 / Frontline) began generating unhandled
errors, returning widespread HTTP 5xx failures. -
At first, Cloudflare suspected a large-scale DDoS attack, but investigation revealed an internal
software issue.
Services Impacted
- Core CDN & security services – widespread HTTP 5xx outages
- Workers KV – elevated errors as gateway services failed
- Dashboard / Login / Authentication – dashboard mostly stable, but login flow
(through Turnstile) was impacted
Timeline of Events (UTC)
| Time | Event |
|---|---|
| 11:05 | Database access change deployed. |
| 11:28 | Errors began as feature file changes propagated. |
| 13:05 | Mitigation for Workers KV / Access bypass implemented. |
| 14:30 | Feature file rollback completed; traffic flow restored. |
| 17:06 | Full service restoration confirmed. |
Why It Matters
Cloudflare sits at the core of much of the world’s web infrastructure—websites, APIs, security systems, and online services rely heavily on it. When Cloudflare goes down, the effects ripple across the entire internet.
- Shows how internal configuration issues can scale into global outages.
- Highlights the importance of safe limits, failover systems, and rollback mechanisms.
- Demonstrates how dependency on a single CDN provider can impact uptime.
- Website owners should review redundancy plans (multi-CDN, caching, fallback systems).
What Cloudflare Is Doing Next
- Hardening ingestion of configuration files, treating them with stricter validation.
- Introducing more global kill switches for features to avoid cascade failures.
- Improving proxy module failure handling to prevent system overload from error logs.
Cloudflare acknowledged:
“Today was Cloudflare’s worst outage since 2019… An outage like today is unacceptable.”
(Source: Cloudflare Blog)
What You Should Do (If You Depend on Cloudflare)
- Check Cloudflare dashboard/logs to confirm whether your services were impacted.
- Evaluate your fallback strategy (multi-CDN, failover, local caching).
- Review security module logs (WAF, Bot Management) around the outage window.
- Communicate with customers if they experienced service disruption.
- Add this incident to your internal post-mortem and resilience checklist.
Conclusion
Even highly engineered systems can fail unexpectedly. The Cloudflare outage on
November 18, 2025 is a reminder that no infrastructure is immune to cascading
issues.
If you operate a service relying on Cloudflare, this is a good moment to review your
dependencies, readiness, and mitigation strategies.
