Vulnerability

CVE-2025-59718

Critical· 9.8KEVCVSS9.8EPSS12%

.rules3/5

Fortinet Multiple Products Improper Verification of Cryptographic Signature Vulnerability

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.

Threat signal

100/100

Severe

Severity

critical

CVSS

9.8

EPSS

12%

Active

KEV

CISA KEV — actively exploited

172d overdue

AffectedFortinet — Multiple Products

Added to KEV

2025-12-16

Federal patch due (BOD 22-01)

2025-12-23

Required action (CISA verbatim)

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Vendor advisory + references

CISA description: “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.”

CVSS

v3.1via NVDOpen in FIRST calculator →

9.8/ 10CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack VectorNetworkExploitable remotely over the internet — no local access needed.
Attack ComplexityLowNo special conditions — exploit works reliably.
Privileges RequiredNoneUnauthenticated — no credentials needed.
User InteractionNoneFully automated — no victim action needed.
ScopeUnchangedImpact contained to the vulnerable component.
Confidentiality ImpactHighTotal disclosure of sensitive data.
Integrity ImpactHighTotal compromise of integrity — full data modification possible.
Availability ImpactHighTotal loss of availability — full DoS possible.

EPSS

Exploit prediction · 30-day horizonFIRST.org →

12.1%

probability of exploitation in next 30 days

p94

higher than 94% of all CVEs

3-day trend↑ 0pp

Above the FIRST 'patch on a priority schedule' threshold.

Vendor VEX

No VEX statements published for CVE-2025-59718. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCAct

Active exploitation with total impact on essential/support systems

exploitation: active
automatable: yes
impact: total
mission: support

Lifecycle

2025-12-16Added to CISA KEVransomware: Unknown
2025-12-16Published
2025-12-23Federal patch due (BOD 22-01)
2026-06-12Last modified2 sources

References

No source-event history recorded yet. New revisions will appear here as ingestors re-fetch this CVE.