New QPACK Flaws Can Crash HTTP/3 Servers, Trigger Up to 4,000-Fold Memory Amplification

A remote attacker who has not logged in can crash many HTTP/3 web servers with a single connection, security firm FoxIO disclosed, releasing working proof-of-concept code. By sending a small batch of compressed HTTP headers that expands in memory to a much larger set, the attacker can force the server to use thousands of times more memory than it received, enough to run a default server