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.

According to the versions of the openssh packages installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

    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.(CVE-2025-26465)

Tenable has extracted the preceding description block directly from the EulerOS openssh security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of openssh installed on the remote host is prior to 7.4p1-22. It is, therefore, affected by a vulnerability as referenced in the ALAS2-2025-2769 advisory.

    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. (CVE-2025-26465)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2025-26465)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote SUSE Linux SLES12 host has packages installed that are affected by a vulnerability as referenced in the SUSE- SU-2025:0744-1 advisory.

    - CVE-2025-26465: Fixed a MitM attack against OpenSSH's VerifyHostKeyDNS-enabled client (bsc#1237040).

    Other bugfixes:

    - Fix usage of local accelerator cards via openssl-ibmca (bsc#1216474, bsc#1218871).
    - Add patches from upstream to change the default value of UpdateHostKeys to Yes (unless VerifyHostKeyDNS     is enabled) (bsc#1222831).
    - Fix hostbased ssh login failing occasionally with 'signature unverified: incorrect signature' by fixing     a typo in patch (bsc#1221123).
    - For now we don't ship the ssh-keycat command, but we need the patch for the other SELinux infrastructure     (bsc#1214788).
    - Attempts to mitigate instances of secrets lingering in memory after a session exits (bsc#1213004,     bsc#1213008, bsc#1186673).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of openssh installed on the remote CBL Mariner 2.0 host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the CVE-2025-26465 advisory.

  - 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. (CVE-2025-26465)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of openssh installed on the remote Azure Linux 3.0 host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the CVE-2025-26465 advisory.

  - 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. (CVE-2025-26465)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLES12 host has packages installed that are affected by a vulnerability as referenced in the SUSE- SU-2025:0659-1 advisory.

    - CVE-2025-26465: Fixed a MitM attack against OpenSSH's VerifyHostKeyDNS-enabled client (bsc#1237040).

    - Add a s390 specific ioctl for ECC hardware support (bsc#1225637):
    - for migration to openssh 8.4: write active/enabled switch over files only if not yet present       (bsc#1220110)

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of FreeBSD installed on the remote host is prior to tested version. It is, therefore, affected by multiple vulnerabilities as referenced in the a8f1ee74-f267-11ef-87ba-002590c1f29c advisory.

    OpenSSH client host verification error (CVE-2025-26465)     ssh(1) contains a logic error that allows an on-path attacker to             impersonate any server during certain conditions when the             VerifyHostKeyDNS option is enabled.
    OpenSSH server denial of service (CVE-2025-26466)     The OpenSSH client and server are both vulnerable to a memory/CPU             denial of service while handling SSH2_MSG_PING packets.
    OpenSSH client host verification error (CVE-2025-26465)     Under specific circumstances, a machine-in-the-middle may impersonate             any server when the client has the VerifyHostKeyDNS option enabled.
    OpenSSH server denial of service (CVE-2025-26466)     During the processing of SSH2_MSG_PING packets, a server may be             subject to a memory/CPU denial of service.

Tenable has extracted the preceding description block directly from the FreeBSD security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote CentOS Linux 9 host has packages installed that are affected by a vulnerability as referenced in the openssh-8.7p1-45.el9 build changelog.

  - 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. (CVE-2025-26465)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Fedora 40 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2025-62f6cb2785 advisory.

    Fix missing error codes set and invalid error code checks in OpenSSH. It     prevents memory exhaustion attack and a MITM attack when VerifyHostKeyDNS     is on (CVE-2025-26465, CVE-2025-26466).

Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLES15 / SLES_SAP15 host has packages installed that are affected by a vulnerability as referenced in the SUSE-SU-2025:0605-1 advisory.

    - CVE-2025-26465: Fixed MitM attack against OpenSSH's VerifyHostKeyDNS-enabled client (bsc#1237040).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

An update of the openssh package has been released.

The version of OpenSSH installed on the remote host is prior to 9.9p2. It is, therefore, affected by a man in the middle (MITM) vulnerability. ssh(1) in OpenSSH versions 6.8p1 to 9.9p1 (inclusive) contained a logic error that allowed an on-path attacker (a.k.a MITM) to impersonate any server when the VerifyHostKeyDNS option is enabled. This option is off by default.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 / openSUSE 15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2025:0585-1 advisory.

    - CVE-2025-26465: Fixed MitM attack against OpenSSH's VerifyHostKeyDNS-enabled client (bsc#1237040).
    - CVE-2025-26466: Fixed DoS attack against OpenSSH's client and server (bsc#1237041).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Ubuntu 16.04 LTS / 18.04 LTS host has packages installed that are affected by a vulnerability as referenced in the USN-7270-2 advisory.

    USN-7270-1 fixed a vulnerability in OpenSSH. This update provides the corresponding update for Ubuntu     16.04 LTS and Ubuntu 18.04 LTS.



Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote host is affected by the vulnerability described in GLSA-202502-01 (OpenSSH: Multiple Vulnerabilities)

    Multiple vulnerabilities have been discovered in OpenSSH. Please review the CVE identifiers referenced     below for details.

Tenable has extracted the preceding description block directly from the Gentoo Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of openssh installed on the remote host is prior to 9.9p2. It is, therefore, affected by multiple vulnerabilities as referenced in the SSA:2025-049-01 advisory.

    New openssh packages are available for Slackware 15.0 and -current to fix security issues.

Tenable has extracted the preceding description block directly from the openssh security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Ubuntu 20.04 LTS / 22.04 LTS / 24.04 LTS / 24.10 host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-7270-1 advisory.

    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. (CVE-2025-26465)

    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. (CVE-2025-26466)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Debian 12 host has packages installed that are affected by a vulnerability as referenced in the dsa-5868 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-5868-1                   security@debian.org     https://www.debian.org/security/                     Salvatore Bonaccorso     February 18, 2025                     https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : openssh     CVE ID         : CVE-2025-26465

    The Qualys Threat Research Unit (TRU) discovered that the OpenSSH client     is vulnerable to a machine-in-the-middle attack if the VerifyHostKeyDNS     option is enabled (disabled by default).

    Details can be found in the Qualys advisory at     https://www.qualys.com/2025/02/18/openssh-mitm-dos.txt

    For the stable distribution (bookworm), this problem has been fixed in     version 1:9.2p1-2+deb12u5.

    We recommend that you upgrade your openssh packages.

    For the detailed security status of openssh please refer to its security     tracker page at:
    https://security-tracker.debian.org/tracker/openssh

    Further information about Debian Security Advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://www.debian.org/security/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Debian 11 host has packages installed that are affected by a vulnerability as referenced in the dla-4057 advisory.

    -------------------------------------------------------------------------     Debian LTS Advisory DLA-4057-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                         Colin Watson     February 18, 2025                             https://wiki.debian.org/LTS
    -------------------------------------------------------------------------

    Package        : openssh     Version        : 1:8.4p1-5+deb11u4     CVE ID         : CVE-2025-26465

    The Qualys Threat Research Unit (TRU) discovered that the OpenSSH client     is vulnerable to a machine-in-the-middle attack if the VerifyHostKeyDNS     option is enabled (disabled by default).

    Details can be found in the Qualys advisory at     https://www.qualys.com/2025/02/18/openssh-mitm-dos.txt

    For Debian 11 bullseye, this problem has been fixed in version     1:8.4p1-5+deb11u4.

    We recommend that you upgrade your openssh packages.

    For the detailed security status of openssh please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/openssh

    Further information about Debian LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS     Attachment:
    signature.asc     Description: PGP signature

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
234154	EulerOS 2.0 SP11 : openssh (EulerOS-SA-2025-1368)	Nessus	Huawei Local Security Checks	medium
234151	EulerOS 2.0 SP11 : openssh (EulerOS-SA-2025-1367)	Nessus	Huawei Local Security Checks	medium
232352	Amazon Linux 2 : openssh (ALAS-2025-2769)	Nessus	Amazon Linux Local Security Checks	medium
231441	Linux Distros Unpatched Vulnerability : CVE-2025-26465	Nessus	Misc.	medium
216960	SUSE SLES12 Security Update : openssh8.4 (SUSE-SU-2025:0744-1)	Nessus	SuSE Local Security Checks	medium
216894	CBL Mariner 2.0 Security Update: openssh (CVE-2025-26465)	Nessus	MarinerOS Local Security Checks	medium
216886	Azure Linux 3.0 Security Update: openssh (CVE-2025-26465)	Nessus	Azure Linux Local Security Checks	medium
216732	SUSE SLES12 Security Update : openssh (SUSE-SU-2025:0659-1)	Nessus	SuSE Local Security Checks	medium
216705	FreeBSD : FreeBSD -- Multiple vulnerabilities in OpenSSH (a8f1ee74-f267-11ef-87ba-002590c1f29c)	Nessus	FreeBSD Local Security Checks	medium
216704	CentOS 9 : openssh-8.7p1-45.el9	Nessus	CentOS Local Security Checks	medium
216684	Fedora 40 : openssh (2025-62f6cb2785)	Nessus	Fedora Local Security Checks	medium
216651	SUSE SLES15 Security Update : openssh (SUSE-SU-2025:0605-1)	Nessus	SuSE Local Security Checks	medium
216579	Photon OS 4.0: Openssh PHSA-2025-4.0-0757	Nessus	PhotonOS Local Security Checks	medium
216524	Photon OS 3.0: Openssh PHSA-2025-3.0-0817	Nessus	PhotonOS Local Security Checks	medium
216523	Photon OS 5.0: Openssh PHSA-2025-5.0-0475	Nessus	PhotonOS Local Security Checks	medium
216476	OpenSSH < 9.9p2 MitM	Nessus	Misc.	medium
216453	SUSE SLED15 / SLES15 / openSUSE 15 Security Update : openssh (SUSE-SU-2025:0585-1)	Nessus	SuSE Local Security Checks	medium
216430	Ubuntu 16.04 LTS / 18.04 LTS : OpenSSH vulnerability (USN-7270-2)	Nessus	Ubuntu Local Security Checks	medium
216429	GLSA-202502-01 : OpenSSH: Multiple Vulnerabilities	Nessus	Gentoo Local Security Checks	medium
216428	Slackware Linux 15.0 / current openssh Multiple Vulnerabilities (SSA:2025-049-01)	Nessus	Slackware Local Security Checks	medium
216422	Ubuntu 20.04 LTS / 22.04 LTS / 24.04 LTS / 24.10 : OpenSSH vulnerabilities (USN-7270-1)	Nessus	Ubuntu Local Security Checks	medium
216407	Debian dsa-5868 : openssh-client - security update	Nessus	Debian Local Security Checks	medium
216406	Debian dla-4057 : openssh-client - security update	Nessus	Debian Local Security Checks	medium

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CVE-2025-26465

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