CVE-2026-116774
russh: peer-declared zero maximum packet size permanently stalls channel writes (silent AsyncWrite hang)
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| rust | russh | >= 0.60.0, <= 0.64.1 | 0.65 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Eugeny | Russh | from 0.60.0, before 0.65.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-fw5c-8223-6h42
- https://github.com/Eugeny/russh/security/advisories/GHSA-fw5c-8223-6h42
- https://nvd.nist.gov/vuln/detail/CVE-2026-116774
- https://github.com/Eugeny/russh/commit/39cb9dbaa37caf555d34c6c22efa3bbbff9e186c
- https://github.com/Eugeny/russh/releases/tag/v0.65.0