CVE-2026-55653

Public on 2026-06-23
Modified on 2026-06-25
Description
A flaw was found in OpenSSH. A malicious SSH server can exploit a double free vulnerability in the Diffie-Hellman Group Exchange (DH-GEX) client path. This occurs during FIPS (Federal Information Processing Standards) mode known-group validation when the client processes attacker-controlled DH-GEX group parameters. Successful exploitation leads to client-side process termination, resulting in a Denial of Service (DoS).
Severity
Medium severity
Medium
See what this means
CVSS v3 Base Score
5.3
See breakdown

Affected Packages

Platform Package Release Date Advisory Status
Amazon Linux 2 - Core openssh Not Affected
Amazon Linux 2023 openssh Pending Fix

CVSS Scores

Score Type Score Vector
Amazon Linux CVSSv3 5.3 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H