CVE-2025-26465

Modified Modified - Updated After Analysis

BaseFortify

Publication date: 2025-02-18

Last updated on: 2026-10-21

Assigner: redhat-SADP

Description

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.

CVSS Scores

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Meta Information

Published

2025-02-18

Last Modified

2026-10-21

Generated

2026-10-23

AI Q&A

2025-02-19

EPSS Evaluated

2026-10-20

NVD

CVE-2025-26465

Affected Vendors & Products

Vendor	Product	Version / Range
debian	debian_linux	11.0
openbsd	openssh	From 6.9 (inc) to 9.8 (inc)
openbsd	openssh	6.8
openbsd	openssh	9.9
openbsd	openssh	9.9
netapp	active_iq_unified_manager	*
netapp	ontap	9
redhat	openshift_container_platform	4.0
debian	debian_linux	12.0
redhat	enterprise_linux	9.0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-390	The product detects a specific error, but takes no actions to handle the error.

Attack-Flow Graph

Executive Summary

CVE-2025-26465 is a vulnerability found in OpenSSH that occurs when the VerifyHostKeyDNS option is enabled. It allows for a machine-in-the-middle attack, where a malicious machine can impersonate a legitimate server. This vulnerability arises from the mishandling of error codes by OpenSSH under specific conditions during host key verification. For an attack to be successful, the attacker must first exhaust the client's memory resources, making the attack complex.

Detection Guidance

To detect this vulnerability, you can check the OpenSSH version running on your systems and verify if the VerifyHostKeyDNS option is enabled. You can use the following commands: 1. Check OpenSSH version: `ssh -V` 2. Check the configuration for VerifyHostKeyDNS: `grep VerifyHostKeyDNS /etc/ssh/sshd_config` or `grep VerifyHostKeyDNS /etc/ssh/ssh_config`.

Impact Analysis

This vulnerability can impact users by exposing them to potential machine-in-the-middle attacks, where an attacker could intercept and manipulate communications between the client and a legitimate server. If successful, this could lead to unauthorized access to sensitive data, data breaches, or other malicious activities.

Compliance Impact

The vulnerability could affect compliance with standards like GDPR and HIPAA by potentially exposing sensitive personal and health information to unauthorized access. If an organization is compromised due to this vulnerability, it may face legal repercussions, fines, and damage to its reputation, as these regulations require strict protection of personal data.

Mitigation Strategies

To mitigate this vulnerability, you should disable the VerifyHostKeyDNS option in your OpenSSH configuration files. You can do this by editing the `/etc/ssh/sshd_config` and/or `/etc/ssh/ssh_config` files and setting `VerifyHostKeyDNS no`. Additionally, consider updating OpenSSH to the latest version where this vulnerability is patched.

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