CVE-2026-73429: Russh: client wrong-length X25519 `clone_from_slice` panic (pre-auth DoS)
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 KEXECDHREPLY containing a server ephemeral value that is not 32 bytes long. The client-side Curve25519Kex::computesharedsecret function in russh/src/kex/curve25519.rs passes the decoded exchange.serverephemeral value to clonefromslice 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
russhto a version that resolves this vulnerability.Fixed in 0.62.4
Event History
Frequently Asked Questions
What is the severity of CVE-2026-73429?
CVE-2026-73429 has a medium severity score of 5.3.
How do I fix CVE-2026-73429?
To fix CVE-2026-73429, upgrade to russh version 0.62.4 or later.
What is the impact of CVE-2026-73429?
CVE-2026-73429 can lead to a pre-authentication denial of service (DoS) by crashing the russh client.
Who is affected by CVE-2026-73429?
Any user of the russh library prior to version 0.62.4 is affected by CVE-2026-73429.
What causes the vulnerability in CVE-2026-73429?
CVE-2026-73429 is caused by handling a malformed KEX_ECDH_REPLY with an incorrect length of the ephemeral value.