CVE-2026-73430

Received Received - Intake

Denial of Service in Russh SSH Library

Publication date: 2026-08-12

Last updated on: 2026-08-12

Assigner: GitHub, Inc.

Description

Russh is a Rust SSH client & server library. Prior to 0.62.4, an unauthenticated SSH client can cause a denial of service by sending SSH_MSG_KEX_ECDH_INIT with a 32-byte all-zero Q_C value. Curve25519Kex::server_dh in russh/src/kex/curve25519.rs accepts the all-zero peer public value and computes an all-zero shared secret, after which compute_exchange_hash calls encode_mpint in russh/src/kex/mod.rs and indexes beyond the end of the input while skipping leading zero bytes. The resulting panic occurs before authentication and terminates the server key-exchange task. This issue is fixed in version 0.62.4.

CVSS Scores

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Meta Information

Published

2026-08-12

Last Modified

2026-08-12

Generated

2026-08-13

AI Q&A

2026-08-13

EPSS Evaluated

N/A

NVD

CVE-2026-73430

Affected Vendors & Products

Currently, no data is known.

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-754	The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product.

Attack-Flow Graph

Executive Summary

This is a denial of service vulnerability in the Russh SSH library. An unauthenticated attacker can send a malformed SSH key exchange message with a zero value, causing the server to crash during the key exchange process before authentication.

Detection Guidance

This vulnerability can be detected by monitoring for crashes or panics in the Russh SSH server during key exchange. Check server logs for SSH_MSG_KEX_ECDH_INIT handling failures or unexpected terminations. No specific commands are provided in the context.

Impact Analysis

If you use Russh library versions before 0.62.4 in an SSH server, an attacker could remotely crash your SSH server by sending a single malicious packet, disrupting legitimate access.

Mitigation Strategies

Upgrade Russh to version 0.62.4 or later to address the issue. If immediate upgrade is not possible, restrict network access to SSH services or implement rate limiting to reduce exposure.

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