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CVE-2019-5591 Fortinet CVE debrief

CVE-2019-5591 is a Fortinet FortiOS vulnerability identified by CISA as known to be exploited and added to the Known Exploited Vulnerabilities catalog on 2021-11-03. The supplied corpus describes it as a Fortinet FortiOS default configuration vulnerability and directs defenders to apply updates per vendor instructions. Because CISA lists it in KEV, organizations using FortiOS should treat it as a high-priority remediation item.

Vendor
Fortinet
Product
FortiOS
CVSS
Unknown
CISA KEV
Listed
Original CVE published
2021-11-03
Original CVE updated
2021-11-03
Advisory published
2021-11-03
Advisory updated
2021-11-03

Who should care

Security teams, firewall and network appliance administrators, and asset owners responsible for Fortinet FortiOS deployments should prioritize this CVE, especially any environment that exposes FortiOS devices or depends on them for perimeter security.

Technical summary

The available source material identifies CVE-2019-5591 only at a high level as a Fortinet FortiOS default configuration vulnerability. CISA’s KEV entry indicates it is known to be exploited and recommends applying updates per vendor instructions. No further technical details are provided in the supplied corpus, so defensive guidance should remain limited to vendor-directed remediation and inventory-based exposure checks.

Defensive priority

High. Inclusion in CISA’s Known Exploited Vulnerabilities catalog indicates active real-world exploitation risk and makes this a remediation priority for affected FortiOS deployments.

Recommended defensive actions

  • Inventory all Fortinet FortiOS assets and confirm whether they are affected by CVE-2019-5591.
  • Apply Fortinet updates and follow vendor instructions referenced by CISA KEV.
  • Verify that configuration baselines and hardening standards are enforced across FortiOS deployments.
  • Prioritize internet-facing or perimeter FortiOS devices for immediate review and remediation.
  • Track remediation status against the CISA KEV due date and internal patch SLAs.

Evidence notes

This debrief is based on the supplied CISA KEV source item and the linked official records. The corpus provides only a short vulnerability label, KEV status, date added (2021-11-03), due date (2022-05-03), and the required action to apply updates per vendor instructions. No additional technical exploit details were available in the supplied material.

Official resources

CISA lists CVE-2019-5591 in the Known Exploited Vulnerabilities catalog, with a KEV date added of 2021-11-03 and a due date of 2022-05-03. The supplied corpus does not include exploit mechanics or deeper technical analysis.