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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
High
Difficult to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v3.1
Weakness Type (CWE)
Vulnerable Products 14
| Configuration | From (including) | Up to (excluding) |
|---|---|---|
|
Openbsd Openssh
cpe:2.3:a:openbsd:openssh:9.5:p1:*:*:*:*:*:*
|
— | — |
|
Openbsd Openssh
cpe:2.3:a:openbsd:openssh:9.6:-:*:*:*:*:*:*
|
— | — |
|
Openbsd Openssh
cpe:2.3:a:openbsd:openssh:9.6:p1:*:*:*:*:*:*
|
— | — |
|
Openbsd Openssh
cpe:2.3:a:openbsd:openssh:9.7:-:*:*:*:*:*:*
|
— | — |
|
Openbsd Openssh
cpe:2.3:a:openbsd:openssh:9.7:p1:*:*:*:*:*:*
|
— | — |
|
Openbsd Openssh
cpe:2.3:a:openbsd:openssh:9.8:-:*:*:*:*:*:*
|
— | — |
|
Openbsd Openssh
cpe:2.3:a:openbsd:openssh:9.8:p1:*:*:*:*:*:*
|
— | — |
|
Openbsd Openssh
cpe:2.3:a:openbsd:openssh:9.9:-:*:*:*:*:*:*
|
— | — |
|
Openbsd Openssh
cpe:2.3:a:openbsd:openssh:9.9:p1:*:*:*:*:*:*
|
— | — |
|
Canonical Ubuntu_Linux
cpe:2.3:o:canonical:ubuntu_linux:24.04:*:*:*:lts:*:*:*
|
— | — |
|
Canonical Ubuntu_Linux
cpe:2.3:o:canonical:ubuntu_linux:24.10:*:*:*:*:*:*:*
|
— | — |
|
Debian Debian_Linux
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
|
— | — |
|
Debian Debian_Linux
cpe:2.3:o:debian:debian_linux:12.0:*:*:*:*:*:*:*
|
— | — |
|
Debian Debian_Linux
cpe:2.3:o:debian:debian_linux:13.0:*:*:*:*:*:*:*
|
— | — |
References 15
https://access.redhat.com/security/cve/CVE-2025-26466
secalert@redhat.com
https://bugzilla.redhat.com/show_bug.cgi?id=2345043
secalert@redhat.com
https://seclists.org/oss-sec/2025/q1/144
secalert@redhat.com
https://www.qualys.com/2025/02/18/openssh-mitm-dos.txt
secalert@redhat.com
http://seclists.org/fulldisclosure/2025/Feb/18
af854a3a-2127-422b-91ae-364da2661108
http://seclists.org/fulldisclosure/2025/May/7
af854a3a-2127-422b-91ae-364da2661108
http://seclists.org/fulldisclosure/2025/May/8
af854a3a-2127-422b-91ae-364da2661108
https://bugzilla.suse.com/show_bug.cgi?id=1237041
af854a3a-2127-422b-91ae-364da2661108
https://security-tracker.debian.org/tracker/CVE-2025-26466
af854a3a-2127-422b-91ae-364da2661108
https://security.netapp.com/advisory/ntap-20250228-0002/
af854a3a-2127-422b-91ae-364da2661108
https://ubuntu.com/security/CVE-2025-26466
af854a3a-2127-422b-91ae-364da2661108
https://www.openwall.com/lists/oss-security/2025/02/18/1
af854a3a-2127-422b-91ae-364da2661108
https://www.openwall.com/lists/oss-security/2025/02/18/4
af854a3a-2127-422b-91ae-364da2661108
https://www.vicarius.io/vsociety/posts/cve-2025-26466-detection-script-memory-c…
af854a3a-2127-422b-91ae-364da2661108
https://www.vicarius.io/vsociety/posts/cve-2025-26466-mitigation-script-memory-…
af854a3a-2127-422b-91ae-364da2661108