Openssh: denial-of-service in openssh

Vulnerability Description

A 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.

References

• https://access.redhat.com/security/cve/CVE-2025-26466
• https://bugzilla.redhat.com/show_bug.cgi?id=2345043
• https://seclists.org/oss-sec/2025/q1/144
• https://www.qualys.com/2025/02/18/openssh-mitm-dos.txt