CVE-2025-26466
Openssh: denial-of-service in openssh
At a glance
- Severity
- MEDIUM 5.9
- EPSS
- EPSS 38.68 % · percentile 99 (2026-10-27)
- State
- PUBLISHED
- Published
- Updated
- Assigner
- redhat
- NVD status
- Modified
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.
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | MEDIUM 5.9 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H | redhat |
| CVSS 3.1 | MEDIUM 5.9 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H | NVD · secalert@redhat.com (Secondary) |
| CVSS 3.1 | MEDIUM 5.9 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H | NVD · nvd@nist.gov (Primary) |
Weaknesses (CWE)
European references
- ENISA EUVD · EUVD-2025-5920
- GCVE · GCVE-0-2025-26466
CERT-FR advisories
- CERTFR-2025-AVI-1021 — Multiples vulnérabilités dans les produits HPE Aruba Networking · cert.ssi.gouv.fr
- CERTFR-2025-AVI-0583 — Multiples vulnérabilités dans les produits Juniper Networks · cert.ssi.gouv.fr
- CERTFR-2025-AVI-0486 — Multiples vulnérabilités dans les produits Qnap · cert.ssi.gouv.fr
- CERTFR-2025-AVI-0393 — Multiples vulnérabilités dans les produits Apple · cert.ssi.gouv.fr
- CERTFR-2025-AVI-0139 — Multiples vulnérabilités dans OpenSSH · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:openbsd:openssh:9.5:p1:*:*:*:*:*:*cpe:2.3:a:openbsd:openssh:9.6:-:*:*:*:*:*:*cpe:2.3:a:openbsd:openssh:9.6:p1:*:*:*:*:*:*cpe:2.3:a:openbsd:openssh:9.7:-:*:*:*:*:*:*cpe:2.3:a:openbsd:openssh:9.7:p1:*:*:*:*:*:*cpe:2.3:a:openbsd:openssh:9.8:-:*:*:*:*:*:*cpe:2.3:a:openbsd:openssh:9.8:p1:*:*:*:*:*:*cpe:2.3:a:openbsd:openssh:9.9:-:*:*:*:*:*:*cpe:2.3:a:openbsd:openssh:9.9:p1:*:*:*:*:*:*cpe:2.3:o:canonical:ubuntu_linux:24.04:*:*:*:lts:*:*:*cpe:2.3:o:canonical:ubuntu_linux:24.10:*:*:*:*:*:*:*cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*cpe:2.3:o:debian:debian_linux:12.0:*:*:*:*:*:*:*cpe:2.3:o:debian:debian_linux:13.0:*:*:*:*:*:*:*
Affected products
| Product | Versions |
|---|---|
| OpenSSH | affected 9.5p1 ≤ 9.9p1 |
| Red Hat · Red Hat Enterprise Linux 10 | unaffected 0:9.9p1-7.el10_0 < * |
| Red Hat · Red Hat Enterprise Linux 9 | unaffected 0:8.7p1-45.el9 < * |
| Red Hat · Red Hat Enterprise Linux 9 | unaffected 0:8.7p1-45.el9 < * |
| Red Hat · Red Hat Enterprise Linux 6 | |
| Red Hat · Red Hat Enterprise Linux 7 | |
| Red Hat · Red Hat Enterprise Linux 8 | |
| Red Hat · Red Hat OpenShift Container Platform 4 | |
| Red Hat · Red Hat OpenShift Container Platform 4 |
References
- https://access.redhat.com/errata/RHBA-2025:6305
- https://access.redhat.com/errata/RHSA-2025:6993
- 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
- https://security.netapp.com/advisory/ntap-20250228-0002/
- https://www.openwall.com/lists/oss-security/2025/02/18/1
- https://www.openwall.com/lists/oss-security/2025/02/18/4
- https://bugzilla.suse.com/show_bug.cgi?id=1237041
- https://security-tracker.debian.org/tracker/CVE-2025-26466
- https://ubuntu.com/security/CVE-2025-26466
- http://seclists.org/fulldisclosure/2025/May/8
- http://seclists.org/fulldisclosure/2025/May/7
- http://seclists.org/fulldisclosure/2025/Feb/18
- https://www.vicarius.io/vsociety/posts/cve-2025-26466-detection-script-memory-consumption-vulnerability-in-openssh
- https://www.vicarius.io/vsociety/posts/cve-2025-26466-mitigation-script-memory-consumption-vulnerability-in-openssh
- https://cert-portal.siemens.com/productcert/html/ssa-398330.html
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |