Pre-authentication Denial of Service attack in OpenSSH - CVE-2025-26466

CVSSv3 Score: 5.9 CVE-2025-26466A flaw was found in the OpenSSH package. For each ping packet the SSH server receives, a pong packet is allocated in a memory buffer and stored in a queue of packages. It is only freed when the server/client key exchange has finished. A malicious client may keep sending such packages, leading to an uncontrolled increase in memory consumption on the server side. Consequently, the server may become unavailable, resulting in a denial of service attack. Revised on 2026-05-25 00:00:00