CVE-2026-73429

Russh: client wrong-length X25519 `clone_from_slice` panic (pre-auth DoS)

State: Published
Severity: 5.3 Medium
Published: Aug 12, 2026
Updated: Aug 14, 2026
Reserved: Aug 12, 2026

Description

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.

Scores

CVSS	Score	Vector	Source
3.1	5.3 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L	GitHub_M

Weaknesses

CWE-704 Incorrect Type Conversion or Cast
CWE-754 Improper Check for Unusual or Exceptional Conditions

Affected Products

Product	Versions
russhEugeny	< 0.62.4Affected

References

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