# CVE-2025-26465: OpenBSD OpenSSH MitM via VerifyHostKeyDNS error mishandling

Source: https://junglewise.ai/threats/cve-2025-26465-openbsd-openssh-mitm-via-verifyhostkeydns-error-mishandling  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2025-02-18. Updated: 2026-05-12  
License: CC BY 4.0 with a link back

CVE-2025-26465 · Severity: medium · CVSS 6.8 · Published 2025-02-18

A vulnerability exists in OpenSSH, a widely used tool for secure remote access to servers. When a specific DNS verification setting is enabled, a sophisticated attacker could potentially intercept and manipulate the connection between a user and a server. This could allow the attacker to impersonate a legitimate server to steal sensitive information or credentials, though the attack is difficult to perform as it requires exhausting the target's system memory first.

Technologies: [Debian Linux](https://junglewise.ai/threats/technologies/debian), [OpenBSD Openssh](https://junglewise.ai/threats/technologies/openssh). Vendors: [Debian](https://junglewise.ai/threats/vendors/debian), [OpenBSD](https://junglewise.ai/threats/vendors/openbsd).

## Quick answers

**Is CVE-2025-26465 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2025-26465 being exploited in the wild.

**How severe is CVE-2025-26465?** Medium severity, with a CVSS score of 6.8, published 18 February 2025.

**Which products and versions are affected?** Debian Linux 11.0, 12.0; OpenBSD Openssh 6.9 through 9.8, 9.9, 9.9p1.

**Is there a fix for CVE-2025-26465?** A patch was published on 2025-02-18: OpenBSD released patch 008_ssh.patch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2025-26465 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2025-26465?** Check whether you run Debian Linux or OpenBSD Openssh at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability (CWE-390) exists in OpenSSH when the 'VerifyHostKeyDNS' option is enabled. The issue stems from the mishandling of error codes during host key verification via DNS. A remote attacker can perform a machine-in-the-middle (MitM) attack by impersonating a legitimate server. To successfully exploit this, the attacker must first trigger a memory exhaustion condition on the client to influence the error handling path. This high complexity requirement mitigates the risk. Patches have been released by OpenBSD (008_ssh.patch) and various Linux distributions including Red Hat and Debian.

## Affected products

- OpenBSD OpenSSH 6.9 through 9.8, 9.9, 9.9p1
- Red Hat Enterprise Linux 8, 9.4
- Debian Debian Linux 11.0, 12.0

## Timeline

- 2025-02-18: disclosed: Vulnerability disclosed by Qualys TRU
- 2025-02-18: advisory
- 2025-02-18: patched: OpenBSD released patch 008_ssh.patch

## References

- [https://access.redhat.com/errata/RHSA-2025:16823](https://access.redhat.com/errata/RHSA-2025:16823)
- [https://access.redhat.com/errata/RHSA-2025:3837](https://access.redhat.com/errata/RHSA-2025:3837)
- [https://access.redhat.com/errata/RHSA-2025:6993](https://access.redhat.com/errata/RHSA-2025:6993)
- [https://access.redhat.com/errata/RHSA-2025:8385](https://access.redhat.com/errata/RHSA-2025:8385)
- [https://access.redhat.com/security/cve/CVE-2025-26465](https://access.redhat.com/security/cve/CVE-2025-26465)
- [https://access.redhat.com/solutions/7109879](https://access.redhat.com/solutions/7109879)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2344780](https://bugzilla.redhat.com/show_bug.cgi?id=2344780)

## Related threats

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- [In sshd in OpenSSH before 10.5, the restrict keyword (in authorized_keys) was supposed to be applicable to tunnel forwarding but was not.](https://junglewise.ai/threats/cve-2026-73283-in-sshd-in-openssh-before-10-5-the-restrict-keyword-in-authorized)
- [In ssh in OpenSSH before 10.5, a use-after-free for realloc data can occur if a certain pair of remote-forwarding operations are concurrent.](https://junglewise.ai/threats/cve-2026-73282-in-ssh-in-openssh-before-10-5-a-use-after-free-for-realloc-data)
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