Summary

Large requests and responses can potentially trigger TCP connection pool crashes due to flow control management in Envoy, and it will impact TCP proxy and HTTP 1 & 2 mixed use cases based on ALPN

Details

It will happen when the connection is closing but upstream data is still coming, resulting in a buffer watermark callback nullptr reference.

PoC

e.g., slow clients send large enough requests and then close the connection to Envoy TCP proxy.

Impact

DoS and crash.