CDN Tsunami Attack Abuses HTTP/3 Translation for Up to 350x DoS Amplification

Researchers have identified two denial-of-service (DoS) attack methods, dubbed "CDN Tsunami," that exploit the translation process between HTTP/3 and HTTP/1.1 used by major content delivery networks. These attacks can amplify low-bandwidth requests into significant loads on origin servers, with amplification factors up to 350x observed on some CDNs. The vulnerabilities affect services like Alibaba, Baidu, Cloudflare, Amazon CloudFront, Fastly, and Tencent, though mitigation strategies are being developed and deployed by some vendors.