| Description: | Netty is an open-source, asynchronous event-driven network application
framework for rapid development of maintainable high performance
protocol servers & clients. In Netty (io.netty:netty-codec-http2)
before version 4.1.60.Final there is a vulnerability that enables
request smuggling. If a Content-Length header is present in the
original HTTP/2 request, the field is not validated by
`Http2MultiplexHandler` as it is propagated up. This is fine as long
as the request is not proxied through as HTTP/1.1. If the request
comes in as an HTTP/2 stream, gets converted into the HTTP/1.1 domain
objects (`HttpRequest`, `HttpContent`, etc.) via
`Http2StreamFrameToHttpObjectCodec `and then sent up to the child
channel's pipeline and proxied through a remote peer as HTTP/1.1 this
may result in request smuggling. In a proxy case, users may assume the
content-length is validated somehow, which is not the case. If the
request is forwarded to a backend channel that is a HTTP/1.1
connection, the Content-Length now has meaning and needs to be
checked. An attacker can smuggle requests inside the body as it gets
downgraded from HTTP/2 to HTTP/1.1. For an example attack refer to the
linked GitHub Advisory. Users are only affected if all of this is
true: `HTTP2MultiplexCodec` or `Http2FrameCodec` is used,
`Http2StreamFrameToHttpObjectCodec` is used to convert to HTTP/1.1
objects, and these HTTP/1.1 objects are forwarded to another remote
peer. This has been patched in 4.1.60.Final As a workaround, the user
can do the validation by themselves by implementing a custom
`ChannelInboundHandler` that is put in the `ChannelPipeline` behind
`Http2StreamFrameToHttpObjectCodec`.
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