CVE-2025-59718 — Fortinet Fortiproxy

What is CVE-2025-59718?

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.

The record classifies CVE-2025-59718 under weakness class CWE-347. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 3 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 323 days ago.

Severity and exploitation probability

CVSS v3.1 base score: 9.8 — CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (FIRST): 68.2% probability of exploitation in the next 30 days, higher than 99.3% of all scored CVEs
CISA KEV: Listed since 2025-12-16, federal remediation deadline 2025-12-23
Threadlinqs priority: 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
Published: 2025-12-09, last modified 2026-08-11

Is CVE-2025-59718 being exploited?

CISA added CVE-2025-59718 to the Known Exploited Vulnerabilities catalog on 2025-12-16, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2025-12-23 under BOD 22-01. Weaponised exploit code for CVE-2025-59718 is publicly available. 2 public proof-of-concept repositories are tracked for this identifier. It currently carries a trending score of 58 in the Threadlinqs vulnerability feed.

exfil0/CVE-2025-59718-PoC (github)
moften/CVE-2025-59718-Fortinet-Poc (github)

Affected products and versions

Fortinet: Fortiproxy, Fortiswitchmanager, Fortios

How to fix CVE-2025-59718

The record marks a vendor fix as available for CVE-2025-59718. Patch reference: https://fortiguard.fortinet.com/psirt/FG-IR-25-573. Vendor advisory: https://fortiguard.fortinet.com/psirt/FG-IR-25-647. Because CVE-2025-59718 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2025-12-23. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

Threat activity tracking CVE-2025-59718

9 tracked threats in the Threadlinqs corpus reference CVE-2025-59718, either in the campaign’s CVE list or as an indicator on the campaign record.

Rapid7 Q3 2026 Threat Landscape: High-Severity Flaws Exploited in 3 Days as The Gentlemen and Qilin Ransomware Dominate — HIGH · 2026-10-21
INC and The Gentlemen Ransomware: Exposed AI-Executed, Human-Approved Attack Infrastructure (Phantom framework) — CRITICAL · 2026-10-20
PEERSTITCH: Stealthy Memory-Resident FortiGate Implant Deployed via FortiManager CVE-2024-47575 by CL-STA-0954 (UNC5820) — CRITICAL · 2026-10-14
FortiBleed: Ongoing Credential-Harvesting Campaign Against Fortinet FortiGate Firewalls and SSL VPN Gateways Feeds INC/Lynx and Payload Ransomware Access (FBI/USSS Alert) — HIGH · 2026-10-06
Multiple Vulnerabilities in Fortigate NGFW on RUGGEDCOM APE1808 Devices (SSA-864900) — Including Actively Exploited FortiCloud SSO Bypass (CVE-2025-59718/-59719) and FortiOS Heap Overflow (CVE-2025-25249) — CRITICAL · 2026-09-13
Edge Infrastructure Under Siege: Tenable and SentinelOne Datasets Reveal Convergent Nation-State and Criminal Exploitation of Perimeter Devices — HIGH · 2026-08-26
FortiBleed: Mass Credential Compromise Campaign Against Internet-Exposed Fortinet FortiGate Devices (86,644 Devices, 194 Countries) — CRITICAL · 2026-07-11
FortiGate SSO Authentication Bypass Campaign (CVE-2025-59718, CVE-2025-59719, CVE-2026-24858) — CRITICAL · 2026-03-10
Fortinet FortiCloud SSO Cross-Tenant Authentication Bypass (CVE-2026-24858) — CRITICAL · 2026-01-27

Sources

Enriched from CVE.org, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on 2026-10-10.