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CVE-2025-59718 — Fortinet FortiOS Auth Bypass

Key facts

CVE-2025-59718 is a Critical vulnerability: Fortinet FortiOS Auth Bypass. This entry ships a detection-only PoC. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2025-12-16), confirming active exploitation in the wild.

Actively exploited — on the CISA KEV catalog

CVE-2025-59718 is listed on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2025-12-16), confirming exploitation in the wild. Federal remediation deadline: 2025-12-23. Prioritise patching and deploy the detection and prevention rules below.
CVE CVE-2025-59718
Severity Critical
CISA KEV Actively exploited (added 2025-12-16)
Detection / prevention —
PoC poc.py
Source 2025/CVE-2025-59718/

Details

Overview

SAML authentication bypass via cryptographic signature flaw

Vulnerability Details

  • CVE ID: CVE-2025-59718
  • CVSS Score: 9.1 (Critical)
  • Type: Auth Bypass
  • Product: Fortinet FortiOS

Affected Products

  • Fortinet FortiOS (specific versions - check vendor advisory)

Proof of Concept

Usage

python3 poc.py -t https://target.com -c
python3 poc.py -t https://target.com -c --version-only

Mitigation

  1. Apply vendor patches immediately
  2. Implement network segmentation
  3. Monitor for exploitation attempts
  4. Review access controls

References

Disclaimer

This PoC is for authorized security testing only.

Frequently asked questions

What is CVE-2025-59718?

CVE-2025-59718 is a Critical vulnerability: Fortinet FortiOS Auth Bypass. This entry ships a detection-only PoC. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2025-12-16), confirming active exploitation in the wild.

How do I detect CVE-2025-59718?

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2025-59718?

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

Is CVE-2025-59718 actively exploited?

Yes. CVE-2025-59718 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, added 2025-12-16, which means it has been exploited in the wild. CISA set a federal remediation deadline of 2025-12-23. Prioritise patching and deploy the detection and prevention rules above.

For authorized security testing and research only. See the full source and NVD record.