Vulnerability Description
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.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/Eugeny/russh/commit/a7fc1eb5717264e31c3c5f7dd849b73989a08f3d
- https://github.com/Eugeny/russh/releases/tag/v0.62.4
- https://github.com/Eugeny/russh/security/advisories/GHSA-5xvq-cp9x-6p6r
FAQ
What is CVE-2026-73430?
CVE-2026-73430 is a vulnerability with a CVSS score of 5.3 (MEDIUM). 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. Curve25519...
How severe is CVE-2026-73430?
CVE-2026-73430 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-73430?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.