Russh: Missing X25519 zero-point validation in hybrid ML-KEM key exchange (CVE-2026-102824) | HOL Guard CVE

Medium · CVSS 4.3CVE-2026-102824

Russh: Missing X25519 zero-point validation in hybrid ML-KEM key exchange

Answer in brief

CVE-2026-102824 records a Medium severity (CVSS 4.3) vulnerability in Russh: Missing X25519 zero-point validation in hybrid ML-KEM key exchange. The current sources do not mark it as known exploited. The current feed maps Eugeny/russh (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

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

Published Sep 29, 2026Updated Sep 29, 2026Source checked Sep 29, 2026First seen by HOL Sep 29, 2026Material review Sep 29, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 4.3
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 4.3. 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 Eugeny/russh (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Eugeny/russhgeneric	<0.63.0	0.63.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for Eugeny/russh.
Review the reported fix. Update Eugeny/russh to 0.63.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 29, 2026

Sources and claim methodology

Upstream source description

Russh is a Rust SSH client and server library. Prior to 0.63.0, the hybrid ML-KEM 768 and X25519 implementation in russh/src/kex/hybrid_mlkem.rs accepts an all-zero 32-byte peer X25519 public key in both server_dh and compute_shared_secret, forcing the X25519 contribution to the combined shared secret to zero. A malicious SSH peer can therefore make the combined secret depend only on ML-KEM, defeating the hybrid exchange's intended fallback protection if ML-KEM is later weakened. This issue is fixed in version 0.63.0.

Quoted source text, attributed separately from HOL analysis.