CVE-2025-59718: Fortinet Multiple Products

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

Yes, if you run Fortinet Multiple Products. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-12-16, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-12-23; treat that as the outer limit, not the target.
EPSS 68.3%, percentile 99: FIRST’s model estimates a 68.3% chance of exploitation activity in the next 30 days, higher than 99% of all scored CVEs (very high). EPSS is a probability, not a verdict.
Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
Editorial verdict: Act now. FortiCloud SSO SAML Bypass: CVE-2025-59718/59719 — If any Fortinet device has FortiCloud SSO admin login turned on, it was open to unauthenticated admin takeover; upgrade, then also apply the January 2026 fix for CVE-2026-24858, which bypassed this patch.

What it is

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.

CISA’s summary

Fortinet FortiOS, FortiSwitchMaster, FortiProxy, and FortiWeb contain an improper verification of cryptographic signature vulnerability that may allow an unauthenticated attacker to bypass the FortiCloud SSO login authentication via a crafted SAML message. Please be aware that CVE-2025-59719 pertains to the same problem and is mentioned in the same vendor advisory. Ensure to apply all patches mentioned in the advisory.

Weakness type: CWE-347.

Product: Fortinet Multiple Products · Assigned by: fortinet · Published: 2025-12-09

Affected and fixed versions

Vendor	Product	Affected versions (per CVE record)
Fortinet	FortiSwitchManager	7.2.0 <= 7.2.6, 7.0.0 <= 7.0.5
Fortinet	FortiOS	7.6.0 <= 7.6.3, 7.4.0 <= 7.4.8, 7.2.0 <= 7.2.11, 7.0.0 <= 7.0.17
Fortinet	FortiProxy	7.6.0 <= 7.6.3, 7.4.0 <= 7.4.10, 7.2.0 <= 7.2.14, 7.0.0 <= 7.0.21

Severity scores

Scored by	CVSS	Score	Vector
fortinet	3.1	9.1 Critical	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C`

Attack vector: network (remotely reachable)
Attack complexity: low
Privileges required: none (no login)
User interaction: none
Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

CISA KEV: added 2025-12-16; federal due date 2025-12-23. Known ransomware use: Unknown.
CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA SSVC assessment: exploitation active, automatable yes, technical impact total.
FIRST EPSS (model of 2026-10-21): 68.29% probability of exploitation activity in the next 30 days; percentile 99.

Timeline

2025-12-09 — CVE record published by fortinet
2025-12-09 — erroneo.us brief: FortiCloud SSO SAML Bypass: CVE-2025-59718/59719
2025-12-16 — Added to CISA’s Known Exploited Vulnerabilities catalog
2025-12-23 — CISA remediation deadline for US federal agencies
2026-10-15 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Other references from the CVE record and advisory

arcticwolf.com arcticwolf.com
cert-portal.siemens.com cert-portal.siemens.com

All exploited Fortinet vulnerabilities · Today’s Security Digest