CVE-2026-102824 Details

A vulnerability exists in the Russh SSH client and server library, specifically in versions prior to 0.63.0. The issue arises in the hybrid ML-KEM 768 and X25519 key exchange implementation, where the library fails to validate that the remote peer's X25519 public key is not the zero point (an all-zero 32-byte value). This oversight allows a malicious SSH peer to nullify the X25519 contribution to the shared secret, effectively reducing the hybrid key exchange to rely solely on ML-KEM. Such an action undermines the intended fallback protection of the hybrid exchange, especially if ML-KEM is later found to be weak.

Users can upgrade to Russh version 0.63.0 or later, where this vulnerability has been addressed. In the patched version, zero-point validation has been added to the hybrid ML-KEM and X25519 key exchange implementation, ensuring that all public keys are properly validated before being used in the key exchange process.