An attacker may cause an HTTP/2 endpoint to read arbitrary amounts of header data by sending an excessive number of CONTINUATION frames. Maintaining HPACK state requires parsing and processing all HEADERS and CONTINUATION frames on a connection. When a request's headers exceed MaxHeaderBytes, no memory is allocated to store the excess headers, but they are still parsed. This permits an malicious user to cause an HTTP/2 endpoint to read arbitrary amounts of header data, all associated with a request which is going to be rejected. These headers can include Huffman-encoded data which is significantly more expensive for the receiver to decode than for an malicious user to send. The fix sets a limit on the amount of excess header frames we will process before closing a connection.
New HTTP/2 DoS attack can crash web servers with a single connection By Bill Toulas April 4, 2024 11:28 AM 0 Newly discovered HTTP/2 protocol vulnerabilities called "CONTINUATION Flood" can lead to denial of service (DoS) attacks, crashing web servers with a single TCP connection in some implementations. HTTP/2 is an update to the HTTP protocol standardized in 2015, designed to improve web performance by introducing binary framing for efficient data transmission, multiplexing to allow multiple r...
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