On Sunday 14 September 2025 at 16:51 UTC, a HTTP/2 rapid reset targeted a healthcare portal customer in Western Europe. The attack peaked at 750.1 million requests per second and lasted 46 minutes. Traffic originated from 2999 autonomous systems in 18 countries, predominantly hijacked home routers.
| Vector | HTTP/2 rapid reset |
| Peak | 750.1 million requests per second |
| Duration | 46 min |
| Time to mitigation | 0.859 s |
| Attack traffic reaching origin | 0.059% |
| Legitimate traffic challenged | 0.43% |
Timeline
The attack was preceded by a hacktivist channel announcing the target. Request rates on the targeted routes exceeded their hourly baseline by a factor of 131 within 36 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
- Enable authenticated origin pulls.
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Review allow-listed partner ranges quarterly.