Exploited CVEs / Fortinet / CVE-2019-5591
CVE-2019-5591
Fortinet FortiOS Default Configuration Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted. Federal agencies were required to remediate by 2022-05-03 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: Fortinet PSIRT Advisories, linked below.
Actively exploited Fortinet FortiOS vulnerability, Medium severity, CVSS 6.5. Added to the CISA KEV catalog 2021-11-03.
Risk summary
Updated July 26, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
Senserva AI Opinion for CVE-2019-5591
A default configuration weakness in Fortinet FortiOS lets an unauthenticated attacker on the same subnet impersonate the LDAP server and intercept credentials the firewall sends for authentication. State-sponsored actors used it, chained with other FortiOS bugs, to harvest VPN credentials per public advisories. Its Medium Severity rating of CVSS 6.5 understates its role as a credential-theft step in confirmed intrusion campaigns.
Do this: Configure LDAPS with server certificate verification on all FortiGate devices and rotate any directory credentials the firewall uses.
AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2019-5591
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for CVE-2019-5591
Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.
CISA required action
Federal (BOD 22-01) remediation due date: 2022-05-03 (past due).
Apply updates per vendor instructions.
Official fix for CVE-2019-5591
The authoritative fix and affected-version list are published by the vendor. Find the FortiOS advisory on Fortinet PSIRT Advisories.
Common questions about CVE-2019-5591
Is CVE-2019-5591 actively exploited?
Yes. CVE-2019-5591 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 19%.
What is the CISA deadline and required action for CVE-2019-5591?
CISA set the federal (BOD 22-01) remediation due date at 2022-05-03, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply updates per vendor instructions.
What fixes CVE-2019-5591?
The authoritative fix is in the vendor advisory: see Fortinet PSIRT Advisories for the patched FortiOS versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.
Can I ask my own AI about CVE-2019-5591?
Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2019-5591's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).
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Authoritative references
Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.
