Bug#1144347: rust-russh: CVE-2026-73429 CVE-2026-73430

Source: rust-russh
Version: 0.57.1-2
Severity: grave
Tags: security upstream
X-Debbugs-Cc: [email protected], Debian Security Team <[email protected]>

Hi,

The following vulnerabilities were published for rust-russh.

CVE-2026-73429[0]:
| Russh is a Rust SSH client & server library. Prior to 0.62.4, a
| malicious SSH server can crash a russh client session with a
| malformed KEX_ECDH_REPLY containing a server ephemeral value that is
| not 32 bytes long. The client-side
| Curve25519Kex::compute_shared_secret function in
| russh/src/kex/curve25519.rs passes the decoded
| exchange.server_ephemeral value to clone_from_slice without
| validating its length, causing a deterministic panic before the
| server host key is verified. The panic terminates the spawned client
| session task and surfaces as a JoinError, while the embedding
| process normally remains running. This issue is fixed in version
| 0.62.4.


CVE-2026-73430[1]:
| Russh is a Rust SSH client & server library. Prior to 0.62.4, an
| unauthenticated SSH client can cause a denial of service by sending
| SSH_MSG_KEX_ECDH_INIT with a 32-byte all-zero Q_C value.
| Curve25519Kex::server_dh in russh/src/kex/curve25519.rs accepts the
| all-zero peer public value and computes an all-zero shared secret,
| after which compute_exchange_hash calls encode_mpint in
| russh/src/kex/mod.rs and indexes beyond the end of the input while
| skipping leading zero bytes. The resulting panic occurs before
| authentication and terminates the server key-exchange task. This
| issue is fixed in version 0.62.4.


If you fix the vulnerabilities please also make sure to include the
CVE (Common Vulnerabilities & Exposures) ids in your changelog entry.

For further information see:

[0] https://security-tracker.debian.org/tracker/CVE-2026-73429
    https://www.cve.org/CVERecord?id=CVE-2026-73429
[1] https://security-tracker.debian.org/tracker/CVE-2026-73430
    https://www.cve.org/CVERecord?id=CVE-2026-73430

Regards,
Salvatore