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.
CVE-2025-26466
CVSS base score
5.9 (v3.1)
Severity
MEDIUM
Attack vector
Network
Weakness
CWE-770
Last modified
November 5, 2026
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products
openbsd openssh
canonical ubuntu linux
debian debian linux
References
- access.redhat.com
- access.redhat.com
- access.redhat.com Third Party Advisory
- bugzilla.redhat.com Issue Tracking
- seclists.org
- www.qualys.com Third Party Advisory
- seclists.org
- seclists.org
- seclists.org
- bugzilla.suse.com Third Party Advisory