Medium 5.9Published Feb 28, 2025

CVE-2025-26466Openssh: denial-of-service in openssh

Updated under an hour ago (Oct 26, 2026, 6:23 PM ET)

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It affects Red Hat Enterprise Linux 10 and 7 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for Red Hat Enterprise Linux 10

Exploited in the last 30 days

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.

CVSS: 5.9 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-770
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: redhat
NVD analysis: Modified
Record last updated: Oct 21, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Red Hat Red Hat Enterprise Linux 10 redhat:enterprise_linux	from 0:9.9p1-7.el10_0 not affected	CNA record
Red Hat Red Hat OpenShift Container Platform 4 redhat:openshift	4	CNA record
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.0 before V3.1.5	CISA ADP
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name)	from V3.1.0 before V3.1.5	CISA ADP
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.0 before V3.1.5	CISA ADP
openbsd openssh openbsd:openssh	9.5; 9.6; 9.6; 9.7; 9.7; 9.8; 9.8; 9.9; and 1 more ranges	NVD
canonical ubuntu_linux canonical:ubuntu_linux	24.04; 24.10	NVD
debian debian_linux debian:debian_linux	11.0; 12.0; 13.0	NVD

References

References

https://access.redhat.com/errata/RHBA-2025:6305	vendor-advisory, x-refsource-redhat
https://access.redhat.com/errata/RHSA-2025:6993	vendor-advisory, x-refsource-redhat
https://access.redhat.com/security/cve/CVE-2025-26466	vdb-entry, x-refsource-redhat, third-party-advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2345043	issue-tracking, x-refsource-redhat
https://seclists.org/oss-sec/2025/q1/144
https://www.qualys.com/2025/02/18/openssh-mitm-dos.txt	third-party-advisory
http://seclists.org/fulldisclosure/2025/Feb/18
http://seclists.org/fulldisclosure/2025/May/7
http://seclists.org/fulldisclosure/2025/May/8
https://bugzilla.suse.com/show_bug.cgi?id=1237041	third-party-advisory
1–10 of 18

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.