CVE-2026-73430: Eugeny Russh

Medium severity, CVSS 5.3. EPSS: 0.6% chance of exploitation in the next 30 days.

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.

Affected products

• Eugeny Russh: before 0.62.4 (fixed in 0.62.4)

Published 2026-08-12. Last modified 2026-09-09.