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

Medium · CVSS 5.3CVE-2026-73429GHSA-G9HV-X236-4QP3

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

Answer in brief

CVE-2026-73429 records a Medium severity (CVSS 5.3) vulnerability in Russh: client wrong-length X25519 `clone_from_slice` panic (pre-auth DoS). The current sources do not mark it as known exploited. The current feed maps russh (crates.io), Eugeny/russh (generic), russh (rust). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 12, 2026Updated Sep 9, 2026Source checked Sep 28, 2026First seen by HOL Aug 12, 2026Material review Sep 9, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 5.3
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps russh (crates.io), Eugeny/russh (generic), russh (rust). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
russhcrates.io	>=0 <0.62.4	0.62.4
Eugeny/russhgeneric	< 0.62.4	Not reported
russhrust	<=0.62.3	0.62.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for russh, Eugeny/russh, russh.
Review the reported fix. Update russh to 0.62.4; russh to 0.62.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 12, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 9, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 12, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.