Http4s Ember HTTP/2: unbounded inbound body buffering

NVD Description

Ember's HTTP/2 stack replenishes the inbound flow-control window based on bytes received off the wire, not bytes consumed by the application. Received DATA is buffered in an unbounded per-stream channel. Flow control therefore provides no backpressure: a peer can stream a large or unbounded body faster than the application drains it and the connection retains every payload in heap. This is the read-path mirror of the [outbound queue issue](https://github.com/http4s/http4s/security/advisories/GHSA-8f3q-3jmv-7prw). This affects an Ember receiving a request body and an Ember client receiving a response body from a hostile server. ### Impact Unauthenticated remote denial of service (OOM) against any Ember server built `.withHttp2` for a non-draining or slow-draining route, and against an Ember client consuming from a hostile or compromised server. ### Workarounds - Disable HTTP/2 to remove the vector entirely. - Apply an aggregate request-entity size limit (e.g. `EntityLimiter` middleware) on routes that consume the body. - Ensure handlers fully drain request bodies with aggressive idle timeouts.

Affected Packages (3)