Double flow control refund on HTTP/2 server streams in net/http

Summary

The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client can exploit this to bypass the configured connection-level flow control limit (MaxReceiveBufferPerConnection). Total buffered data is still limited by the concurrent stream limit and stream-level flow control.

Affected versions

• net/http

  fixed in 1.26.9

• net/http/internal/http2

  From 1.27.0-0 · fixed in 1.27.2

• golang.org/x/net/http2

  fixed in 0.60.0

• stdlibGo

  fixed in 1.26.9

• stdlibGo

  From 1.27.0-0 · fixed in 1.27.2

• golang.org/x/netGo

  fixed in 0.60.0

References 6