Hidden HTTP 2
Summary: PortSwigger Research describes misconfigured servers that support HTTP/2 but fail to advertise it via the ALPN field during the TLS handshake, so clients default to HTTP/1.1 and the HTTP/2 support stays hidden. The result is that testers overlook viable HTTP/2 attack surface and miss associated vulnerabilities such as HTTP/2 downgrade-based request smuggling.
Key Takeaway: An entire class of request smuggling bugs sits behind a protocol your scanners may never probe, because the server never told them HTTP/2 was there.
Read the original at PortSwigger Research ↗
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