A flaw was found in the OpenSSH package. For each ping packet the SSH server receives, a pong packet is allocated in a memory buffer and stored in a queue of packages. It is only freed when the server/client key exchange has finished. A malicious client may keep sending such packages, leading to an uncontrolled increase in memory consumption on the server side. Consequently, the server may become unavailable, resulting in a denial of service attack.

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 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 version of OpenSSH installed on the remote host is prior to 9.9p2. It is, therefore, affected by a vulnerability as referenced in the release-9.9p2 advisory. sshd(8) in OpenSSH versions 9.5p1 to 9.9p1 (inclusive) is vulnerable to a memory/CPU denial-of-service related to the handling of SSH2_MSG_PING packets. This condition may be mitigated using the existing PerSourcePenalties feature.

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 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.

ID	Name	Product	Family	Severity
216705	FreeBSD : FreeBSD -- Multiple vulnerabilities in OpenSSH (a8f1ee74-f267-11ef-87ba-002590c1f29c)	Nessus	FreeBSD Local Security Checks	medium
216684	Fedora 40 : openssh (2025-62f6cb2785)	Nessus	Fedora Local Security Checks	medium
216475	OpenSSH < 9.9p2 DoS	Nessus	Misc.	medium
216453	SUSE SLED15 / SLES15 / openSUSE 15 Security Update : openssh (SUSE-SU-2025:0585-1)	Nessus	SuSE 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

Detections

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CVE-2025-26466

medium

Tenable Plugins

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medium