Background exploitation KEV catalog Ransomware
CVE-2019-5591

Fortinet FortiOS Default Configuration Vulnerability

A Default Configuration vulnerability in FortiOS may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the LDAP server.

CheckOps priority index
5.6/10 Patch within 7 days
Severity6.5
Probability1.9
Exploitation4/5

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

EPSS · today 18.6% higher than 97.3% of CVEs
CVSS 3.1 6.5 AV:A/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 4 / 5

  • KEV catalog (CISA)03 Nov 2021
  • Exploited in EUVD (ENISA)03 Nov 2021
  • Used by ransomwareyes
  • EPSS above 10 %18.6%
  • No account, over the networkno

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

Affected products

Fortinet FortiOSFortiOS
Affected versions
  • FortiOS 6.2.0 and below.
Weaknesses (CWE)

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: 18.6%

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

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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