What’s Vulnerable › Vulnerabilities

CVE-2026-73430: Russh: Pre-auth remote panic via all-zero Curve25519 peer public value (encode_mpint OOB)

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-12 · updated 2026-10-24
• Weakness: CWE-754

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.

Affected products

• Eugeny russh: before 0.62.4

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

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