The HTTP/2 server incorrectly refunds connection-level flow control twice for the same data. This occurs when a client resets a stream, refunding data for the sent-but-unread portion, and again when a request handler reads that buffered data. A malicious client can use this behavior to bypass the `MaxReceiveBufferPerConnection` connection-level flow control limit. Total buffered data remains limited by the stream-level flow control and the concurrent stream limit.