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Known exploited vulnerability · CISA KEV

CVE-2025-59718: 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.

CVE-2025-59718

Exploited in the wild. Fix this first.

CISA added it to the Known Exploited Vulnerabilities catalog on 2025-12-16: attackers are using it right now.

CISA KEV
Listed
Added 2025-12-16 · federal fix-by 2025-12-23
EPSS (30 days)
68%
Higher than 99.3% of CVEs · 2026-11-01
CVSS
No score

What CISA says

Fortinet Multiple Products Improper Verification of Cryptographic Signature Vulnerability

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

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How to check if you are exposed to CVE-2025-59718

  1. Find every Fortinet Multiple Products system you or your clients run, including ones exposed to the internet. Those come first: CISA only lists flaws attackers are already using.
  2. Compare each version with the fixed versions in the vendor advisory below. Where no fix exists yet, apply the vendor’s mitigation or take the system off the internet.
  3. Run a credentialed vulnerability scan to catch the systems you missed, then check that the next scan no longer reports CVE-2025-59718.

US federal agencies had to fix this by 2025-12-23. Everyone else should treat that deadline as a guide: if it has passed, this is overdue.

Timeline

  1. · Added to CISA's Known Exploited Vulnerabilities catalog
  2. · Fix-by date for US federal agencies, passed 313 days ago

Vendor advisories and fixes

Weakness type

More exploited Fortinet vulnerabilities

CISA lists 32 exploited Fortinet vulnerabilities. The closest matches:

Keep going

Sources: CISA Known Exploited Vulnerabilities catalog (version 2026.10.30); EPSS data from FIRST.org; CVSS and descriptions from the NIST National Vulnerability Database. Checked 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

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