CVE-2025-26465

Openssh: machine-in-the-middle attack if verifyhostkeydns is enabled

Severity Score

6.8

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

Attend

*SSVC

Descriptions

A vulnerability was found in OpenSSH when the VerifyHostKeyDNS option is enabled. A machine-in-the-middle attack can be performed by a malicious machine impersonating a legit server. This issue occurs due to how OpenSSH mishandles error codes in specific conditions when verifying the host key. For an attack to be considered successful, the attacker needs to manage to exhaust the client's memory resource first, turning the attack complexity high.

It was discovered that the OpenSSH client incorrectly handled the non-default VerifyHostKeyDNS option. If that option were enabled, an attacker could possibly impersonate a server by completely bypassing the server identity check. It was discovered that OpenSSH incorrectly handled the transport-level ping facility. A remote attacker could possibly use this issue to cause OpenSSH clients and servers to consume resources, leading to a denial of service. This issue only affected Ubuntu 24.04 LTS and Ubuntu 24.10.

*Credits: N/A

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Attack Vector

Network

Attack Complexity

High

Authentication

None

Confidentiality

Complete

Integrity

Complete

Availability

None

* Common Vulnerability Scoring System

SSVC

Decision:Attend

Exploitation

Poc

Automatable

Tech. Impact

Total

* Organization's Worst-case Scenario

Timeline

2025-02-10 CVE Reserved
2025-02-18 CVE Published
2025-02-19 First Exploit
2025-05-04 EPSS Updated
2025-05-13 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date

CWE

CWE-390: Detection of Error Condition Without Action

CAPEC

References (17)

URL	Tag	Source
https://blog.qualys.com/vulnerabilities-threat-research/2025/02/18/qualys-tru-discovers-two-vulnerabilities-in-openssh-cve-2025-26465-cve-2025-26466
https://bugzilla.suse.com/show_bug.cgi?id=1237040
https://ftp.openbsd.org/pub/OpenBSD/patches/7.6/common/008_ssh.patch.sig
https://lists.debian.org/debian-lts-announce/2025/02/msg00020.html
https://lists.mindrot.org/pipermail/openssh-unix-announce/2025-February/000161.html
https://security-tracker.debian.org/tracker/CVE-2025-26465
https://ubuntu.com/security/CVE-2025-26465
https://www.openssh.com/releasenotes.html#9.9p2
https://www.openwall.com/lists/oss-security/2025/02/18/1
https://www.openwall.com/lists/oss-security/2025/02/18/4
https://www.theregister.com/2025/02/18/openssh_vulnerabilities_mitm_dos

URL	Date	SRC
https://github.com/rxerium/CVE-2025-26465	2025-02-19
https://github.com/dolutech/patch-manual-CVE-2025-26465-e-CVE-2025-26466	2025-02-21

URL	Date	SRC

URL	Date	SRC
https://access.redhat.com/security/cve/CVE-2025-26465	2025-02-19
https://bugzilla.redhat.com/show_bug.cgi?id=2344780	2025-02-19
https://access.redhat.com/errata/RHSA-2025:3837	2025-05-13
https://access.redhat.com/errata/RHSA-2025:6993	2025-05-13

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Centos Search vendor "Centos"		Centos Search vendor "Centos" for product "Centos"				*		-		Affected
Netapp Search vendor "Netapp"		Active Iq Unified Manager Search vendor "Netapp" for product "Active Iq Unified Manager"				*		-		Affected
Netapp Search vendor "Netapp"		Ontap Search vendor "Netapp" for product "Ontap"				*		-		Affected
Openbsd Search vendor "Openbsd"		Openssh Search vendor "Openbsd" for product "Openssh"				*		-		Affected
Red Hat Search vendor "Red Hat"		Enterprise Linux Search vendor "Red Hat" for product "Enterprise Linux"				*		-		Affected
Redhat Search vendor "Redhat"		Enterprise Linux Search vendor "Redhat" for product "Enterprise Linux"				*		-		Affected
Redhat Search vendor "Redhat"		Openshift Search vendor "Redhat" for product "Openshift"				*		-		Affected
Redhat Search vendor "Redhat"		Openshift Container Platform Search vendor "Redhat" for product "Openshift Container Platform"				*		-		Affected
Redhat Search vendor "Redhat"		Rhel Eus Search vendor "Redhat" for product "Rhel Eus"				*		-		Affected
Amazon Search vendor "Amazon"		Linux Search vendor "Amazon" for product "Linux"				*		-		Affected
Canonical Search vendor "Canonical"		Ubuntu Linux Search vendor "Canonical" for product "Ubuntu Linux"				*		-		Affected
Debian Search vendor "Debian"		Debian Linux Search vendor "Debian" for product "Debian Linux"				*		-		Affected
Fedoraproject Search vendor "Fedoraproject"		Fedora Search vendor "Fedoraproject" for product "Fedora"				*		-		Affected
Freebsd Search vendor "Freebsd"		Freebsd Search vendor "Freebsd" for product "Freebsd"				*		-		Affected
Huawei Search vendor "Huawei"		Euleros Search vendor "Huawei" for product "Euleros"				*		-		Affected
Opensuse Search vendor "Opensuse"		Leap Search vendor "Opensuse" for product "Leap"				*		-		Affected
Redhat Search vendor "Redhat"		Enterprise Linux Search vendor "Redhat" for product "Enterprise Linux"				*		-		Affected
Redhat Search vendor "Redhat"		Rhel Eus Search vendor "Redhat" for product "Rhel Eus"				*		-		Affected
Siemens Search vendor "Siemens"		Simatic S7-1500 Cpu 1518-4 Pn/dp Mfp Firmware Search vendor "Siemens" for product "Simatic S7-1500 Cpu 1518-4 Pn/dp Mfp Firmware"				*		-		Affected
Siemens Search vendor "Siemens"		Simatic S7-1500 Cpu 1518f-4 Pn/dp Mfp Firmware Search vendor "Siemens" for product "Simatic S7-1500 Cpu 1518f-4 Pn/dp Mfp Firmware"				*		-		Affected
Siemens Search vendor "Siemens"		Siplus S7-1500 Cpu 1518-4 Pn/dp Mfp Firmware Search vendor "Siemens" for product "Siplus S7-1500 Cpu 1518-4 Pn/dp Mfp Firmware"				*		-		Affected
Slackware Search vendor "Slackware"		Slackware Linux Search vendor "Slackware" for product "Slackware Linux"				*		-		Affected
Suse Search vendor "Suse"		Sle-module-basesystem Search vendor "Suse" for product "Sle-module-basesystem"				*		-		Affected
Suse Search vendor "Suse"		Sle-module-desktop-applications Search vendor "Suse" for product "Sle-module-desktop-applications"				*		-		Affected
Suse Search vendor "Suse"		Sle Hpc-espos Search vendor "Suse" for product "Sle Hpc-espos"				*		-		Affected
Suse Search vendor "Suse"		Sle Hpc-ltss Search vendor "Suse" for product "Sle Hpc-ltss"				*		-		Affected
Suse Search vendor "Suse"		Sles-ltss-extended-security Search vendor "Suse" for product "Sles-ltss-extended-security"				*		-		Affected
Suse Search vendor "Suse"		Sles-ltss Search vendor "Suse" for product "Sles-ltss"				*		-		Affected
Suse Search vendor "Suse"		Sles Sap Search vendor "Suse" for product "Sles Sap"				*		-		Affected
Suse Search vendor "Suse"		Suse-manager-proxy Search vendor "Suse" for product "Suse-manager-proxy"				*		-		Affected
Suse Search vendor "Suse"		Suse-manager-server Search vendor "Suse" for product "Suse-manager-server"				*		-		Affected