CDN Tsunami DoS Attack Exploits HTTP/3 to 350x Amplification via HTTP/1.1 Conversion

A new DoS attack called 'CDN Tsunami' exploits HTTP/3 to HTTP/1.1 translation mismatches in CDNs, achieving up to 350x bandwidth amplification through QPACK header compression and connection exhaustion techniques. Researchers identified two variants (HBA and HCA) affecting major CDNs, with mitigations applied at the CDN layer rather than origin servers.

Cybersecurity researchers have disclosed two denial-of-service (DoS) attacks that exploit how major content delivery networks (CDNs) convert client-facing HTTP/3 traffic into HTTP/1.1 requests to the websites they front, amplifying a low-bandwidth request stream by up to 350x against the origin server.

The attacks, collectively named "CDN Tsunami," were evaluated against Alibaba, Baidu,

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