Known exploited · Fortinet
CVE-2025-59718: Fortinet Multiple Products Improper Verification of Cryptographic Signature Vulnerability
What it is
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.
- Vendor
- Fortinet
- Product
- Multiple Products
- Added to KEV
- December 16, 2025
- CISA due date
- December 23, 2025
- Ransomware use
- Unknown
What CISA requires
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Forensic triage
No
What to do now
- Find every instance of Multiple Products you run, including the forgotten ones, and check its version against the vendor advisory.
- Apply the vendor's fix or mitigation, before December 23, 2025 if you are bound by CISA's deadline, sooner if it faces the internet.
- Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
References
H2 Security
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Start freeSource: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.