CVE-2026-73430

Name of the Vulnerable Software and Affected Versions Russh versions prior to 0.62.4

Description An unauthenticated SSH client can trigger a denial of service by sending an SSH MSG KEX ECDH INIT message containing a 32-byte all-zero Q C value. The Curve25519Kex::server dh() function in russh/src/kex/curve25519.rs accepts this all-zero peer public value and calculates an all-zero shared secret. Subsequently, the compute exchange hash() function calls encode mpint() in russh/src/kex/mod.rs, which indexes beyond the end of the input while attempting to skip leading zero bytes. This leads to a panic that occurs before authentication, terminating the server key-exchange task.

Recommendations Update to version 0.62.4.