russh: peer-declared zero maximum packet size permanently stalls channel writes (silent AsyncWrite hang)

[ Description ]Official description

russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. From 0.60.0 until 0.65.0, channel-open parsing accepts a peer-declared maximum_packet_size of zero and passes it into ChannelTx::poll_writable in russh/src/channels/io/tx.rs. The Channel::data, Channel::make_writer, and Channel::into_stream asynchronous write paths then calculate a writable size of zero and remain pending forever because window adjustments cannot satisfy a static zero packet maximum. An authenticated client can strand server writes, and a malicious server can strand client writes, allowing affected tasks, channels, and connections to accumulate without surfacing an error. This issue is fixed in version 0.65.0.

[ Fixes ]Fixes and patches

• russh 0.65Fixed version · GitHub Advisories · rust package russh: upgrade to 0.65 or later (affected >= 0.60.0, <= 0.64.1)

[ Packages ]Affected open-source packages

• russh rustAffected >= 0.60.0, <= 0.64.1 · fixed in 0.65 · GHSA-fw5c-8223-6h42

[ References ]References

• github.com/Eugeny/russh/commit/39cb9dbaa37caf555d34c6c22efa3bbbff9e186c
• github.com/Eugeny/russh/releases/tag/v0.65.0
• github.com/Eugeny/russh/security/advisories/GHSA-fw5c-8223-6h42