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Fortinet Fortigate SSO Login Authentication Bypass (FG-IR-25-647)

critical Nessus Plugin ID 277980

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Synopsis

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

Description

The version of Fortigate installed on the remote host is prior to tested version. It is, therefore, affected by multiple vulnerabilities as referenced in the FG-IR-25-647 advisory.

 - An improper verification of cryptographic signature vulnerability in Fortinet FortiWeb 8.0.0,...
 (CVE-2025-59719)

 - A improper verification of cryptographic signature vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, FortiOS 7.2.0 through 7.2.11, FortiOS 7.0.0 through 7.0.17, FortiProxy 7.6.0 through 7.6.3, FortiProxy 7.4.0 through 7.4.10, FortiProxy 7.2.0 through 7.2.14, FortiProxy 7.0.0 through 7.0.21, FortiSwitchManager 7.2.0 through 7.2.6, FortiSwitchManager 7.0.0 through 7.0.5 allows an unauthenticated attacker to bypass the FortiCloud SSO login authentication via a crafted SAML response message. (CVE-2025-59718)

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

Solution

For 7.0.x, upgrade to Fortigate version 7.0.18 or later. For 7.2.x, upgrade to Fortigate version 7.2.12 or later. For 7.4.x, upgrade to Fortigate version 7.4.9 or later. For 7.6.x, upgrade to Fortigate version 7.6.4 or later.

See Also

https://www.fortiguard.com/psirt/FG-IR-25-647

Plugin Details

Severity: Critical

ID: 277980

File Name: fortigate_FG-IR-25-647.nasl

Version: 1.3

Type: local

Family: Firewalls

Published: 12/9/2025

Updated: 12/16/2025

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Critical

Score: 9.4

CVSS v2

Risk Factor: Critical

Base Score: 10

Temporal Score: 8.3

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

CVSS Score Source: CVE-2025-59719

CVSS v3

Risk Factor: Critical

Base Score: 9.8

Temporal Score: 9.1

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

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

Vulnerability Information

CPE: cpe:/o:fortinet:fortios

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

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 12/9/2025

Vulnerability Publication Date: 12/9/2025

CISA Known Exploited Vulnerability Due Dates: 12/23/2025

Reference Information

CVE: CVE-2025-59718, CVE-2025-59719

IAVA: 2025-A-0770