FRDE Sign in Free trial
Background exploitation KEV catalog Ransomware No authentication
CVE-2020-12812

Fortinet FortiOS SSL VPN Improper Authentication Vulnerability

An improper authentication vulnerability in SSL VPN in FortiOS 6.4.0, 6.2.0 to 6.2.3, 6.0.9 and below may result in a user being able to log in successfully without being prompted for the second factor of authentication (FortiToken) if…

CheckOps priority index
7.4/10 Patch within 7 days
Severity7.5
Probability4.5
Exploitation5/5

Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.

EPSS · today 45.4% higher than 98.8% of CVEs
CVSS 3.1 7.5 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:
Exploited for 1,826 days 03 Nov 2021
CISA due date 03 May 2022 for US federal agencies

Exploitation probability EPSS · FIRST

05010026 Sep05 Oct15 Oct24 Oct02 Nov
EPSS probability (%)Percentile among all CVEs

Exploitation signals 5 / 5

  • KEV catalog (CISA)03 Nov 2021
  • Exploited in EUVD (ENISA)03 Nov 2021
  • Used by ransomwareyes
  • EPSS above 10 %45.4%
  • No account, over the networkyes

What to do

Fix

Apply the vendor’s fix as soon as it is available.

CISA guidance: Apply updates per vendor instructions.

Meanwhile

Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.

Manufacturers (CRA)

Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained

Description ENISA EUVD

An improper authentication vulnerability in SSL VPN in FortiOS 6.4.0, 6.2.0 to 6.2.3, 6.0.9 and below may result in a user being able to log in successfully without being prompted for the second factor of authentication (FortiToken) if they changed the case of their username.

Affected products

Fortinet FortiOSFortiOS
Affected versions
  • FortiOS 6.4.0, 6.2.0 to 6.2.3, 6.0.9 and below
Weaknesses (CWE)
CWE-178CWE-287

Open source packages OSV

Affected libraries according to OSV, with fixed versions.

Timeline

  1. Published

  2. Exploitation reported (ENISA)

  3. Added to the KEV catalog

  4. CISA remediation due date

  5. EPSS peak: 49.3%

References

Other exploited vulnerabilities from the same vendor

  • CVE-2025-61624Fortinet Multiple Products Path Traversal Vulnerability
    3.4 · Rising fast
  • CVE-2026-104286Fortinet FortiMail Path Traversal Vulnerability
    5.9 · Actively exploited
  • CVE-2025-25249Fortinet Multiple Products Heap-based Buffer Overflow Vulnerability
    4.9 · Actively exploited
  • CVE-2025-68686Fortinet FortiOS Exposure of Sensitive Information to an Unauthorized Actor Vulnerability
    5.4 · Actively exploited
  • CVE-2026-39808Fortinet FortiSandbox OS Command Injection Vulnerability
    8.8 · Actively exploited
  • CVE-2026-25089Fortinet FortiSandbox OS Command Injection Vulnerability
    8.3 · Actively exploited

Are you affected?

CheckOps reads your SBOMs and scans, and alerts you as soon as one of your dependencies is exploited.

Get notified at launch

Sources: CISA KEV · ENISA EUVD · FIRST EPSS · OSV. Public data aggregated by CheckOps, updated automatically. Source texts remain the property of their authors. All exploited vulnerabilities