On Sunday 21 June 2026 at 04:40 UTC, a HTTP/2 rapid reset targeted a online payments customer in Western Europe. The attack peaked at 903.4 million requests per second and lasted 40 minutes. Traffic originated from 812 autonomous systems in 72 countries, predominantly compromised cloud VMs.
| Vector | HTTP/2 rapid reset |
| Peak | 903.4 million requests per second |
| Duration | 40 min |
| Time to mitigation | 0.528 s |
| Attack traffic reaching origin | 0.088% |
| Legitimate traffic challenged | 0.36% |
Timeline
The attack was preceded by no stated motive. Request rates on the targeted routes exceeded their hourly baseline by a factor of 233 within 7 seconds. The risk score of participating clients crossed the challenge threshold automatically and proof-of-work difficulty rose with origin load.
What the customer saw
Checkout conversion was unchanged compared with the same hour of the previous week.
Recommendations
- Review allow-listed partner ranges quarterly.
- Add a dedicated rate limit for the targeted route.
- Keep origin IPs out of public DNS history.
The point about origin IPs leaking through certificate transparency logs is underrated.