CVE-2025-26465
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.
Statement
This issue is rated as a moderate severity vulnerability instead of important because it requires specific conditions to be exploitable. First, the OpenSSH client must have the VerifyHostKeyDNS option enabled, which is disabled by default in Red Hat Enterprise Linux (RHEL).
Additionally, while the attack allows a machine-in-the-middle (MITM) adversary to trick the client into accepting an incorrect host key, it does not directly lead to code execution or immediate system compromise. Instead, the attack requires additional steps, such as credential interception or session hijacking to fully exploit the breach.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.8 | 6.8 | 6.8 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | High | High |
| Privileges Required | None | None | None |
| User Interaction | Required | Required | Required |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | High | High | High |
| Integrity Impact | High | High | High |
| Availability Impact | None | None | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
NVD: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Integrity,Other
Technical Impact: Varies by Context; Unexpected State; Alter Execution Logic
An attacker could utilize an ignored error condition to place the system in an unexpected state that could lead to the execution of unintended logic and could cause other unintended behavior.
Frequently Asked Questions
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