Vulnerability · Published Aug 12, 2026 · Assigned by GitHub_M

CVE-2026-73429Russh: client wrong-length X25519 `clone_from_slice` panic (pre-auth DoS)

Medium 5.3

In plain English

A medium-severity security flaw in russh from Eugeny. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 43% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.3Medium

Exploit odds (30 days)0.5%top 56.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:14	rust-russh	0.64.1-1	DEBIAN-CVE-2026-73429
Ubuntu:26.10	rust-russh	no fix listed	UBUNTU-CVE-2026-73429

Affected products (as reported)

Vendor	Product	Versions
Eugeny	russh	< 0.62.4

Weakness: CWE-704, CWE-754 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References

https://github.com/Eugeny/russh/security/advisories/GHSA-g9hv-x236-4qp3 x_refsource_CONFIRM
https://github.com/Eugeny/russh/commit/a7fc1eb5717264e31c3c5f7dd849b73989a08f3d x_refsource_MISC
https://github.com/Eugeny/russh/releases/tag/v0.62.4 x_refsource_MISC