Panic due to large headers in net/http and golang.org/x/net/http/httpguts

A malicious HTTP server or client can cause the net/http client or server to panic.

ReadRequest and ReadResponse can hit an unrecoverable panic when reading a very large header (over 7MB on 64-bit architectures, or over 4MB on 32-bit ones). Transport and Client are vulnerable and the program can be made to crash by a malicious server. Server is not vulnerable by default, but can be if the default max header of 1MB is overridden by setting Server.MaxHeaderBytes to a higher value, in which case the program can be made to crash by a malicious client.

This also affects golang.org/x/net/http2/h2c and HeaderValuesContainsToken in golang.org/x/net/http/httpguts.