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Fortinet FortiManager Pre-authentication DoS attack in OpenSSH - CVE-2025-26466 (FG-IR-25-122)

medium Nessus Plugin ID 275779

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Synopsis

Fortinet Firewall is missing one or more security-related updates.

Description

The version of FortiManager installed on the remote host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the FG-IR-25-122 advisory.

 - 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. (CVE-2025-26466)

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

Solution

For 6.4.x / 7.0.x, see vendor advisory. For 7.2.x, upgrade to FortiManager version 7.2.11 or later. For 7.4.x, upgrade to FortiManager version 7.4.7 or later. For 7.6.x, upgrade to FortiManager version 7.6.3 or later.

See Also

https://www.fortiguard.com/psirt/FG-IR-25-122

https://www.qualys.com/2025/02/18/openssh-mitm-dos.txt

Plugin Details

Severity: Medium

ID: 275779

File Name: fortimanager_FG-IR-25-122.nasl

Version: 1.1

Type: local

Family: Firewalls

Published: 11/19/2025

Updated: 11/19/2025

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v2

Risk Factor: Medium

Base Score: 5.4

Temporal Score: 4.2

Vector: CVSS2#AV:N/AC:H/Au:N/C:N/I:N/A:C

CVSS Score Source: CVE-2025-26466

CVSS v3

Risk Factor: Medium

Base Score: 5.9

Temporal Score: 5.3

Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:fortinet:fortimanager

Required KB Items: Host/Fortigate/model, Host/Fortigate/version

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 3/11/2025

Vulnerability Publication Date: 12/12/2023

Reference Information

CVE: CVE-2025-26466