HTTP Request Smuggling
Attacker exploiterar disagreement mellan front-end-proxy och back-end-server om HTTP-message-boundaries. CL.TE, TE.CL, TE.TE-varianter. Smuggla request förbi WAF + andra-users prefix-payload till victim-request.
James Kettle (PortSwigger) populariserade 2019 med detaljerad research. Real-world: AWS S3, PayPal, Slack hade smuggling-bugs disclosed. Mitigation: front-end + back-end ska enforce strict-HTTP-parsing, prefer HTTP/2 end-to-end (HTTP/2 har clearer framing). Defense in depth: avstå reuse av back-end-connections, validate Transfer-Encoding + Content-Length. Modern: HTTP/2 + HTTP/3 har less smuggling-surface men har egna issues (h2c smuggling, cache-poisoning).