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Fencer Vulns
medium 6.5

CVE-2019-5591 kev+ ransomware in the critical feed json

A Default Configuration vulnerability in FortiOS may allow an unauthenticated attacker on the same subnet to intercept sensitive informatio…

published 2020-08-14 6 y ago modified 2026-08-15 2 mo ago also EUVD-2019-15166

cvss
6.5
version 3.1, CNA
cisa kev
Exploited
added 2021-11-03, used in ransomware
epss
18.6%
EPSS 18.6% chance of exploitation in 30 days, percentile 97%
public exploits
0
none known, plus a Nuclei check

Summary

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

Patch / fix

cisa required action Apply updates per vendor instructions.

Timeline

  1. Published
  2. CISA SSVC: exploitation active
  3. Added to CISA KEV
  4. CISA patch deadline

Known exploited

Added
5 y ago
Patch by
2022-05-03 (4 y ago)
Ransomware
Known to be used in ransomware campaigns
Required action
Apply updates per vendor instructions.
Vendor, product
Fortinet, FortiOS
CISA name
Fortinet FortiOS Default Configuration Vulnerability

Ransomware

Groups reported to have exploited it in intrusions.

  • Nemesis Kitten suspected state-sponsored

reported by secureworks.com

Ransomware Vulnerability Matrix by BushidoUK (github.com/BushidoUK/Ransomware-Vulnerability-Matrix), reformatted per CVE. CC BY 4.0

ATT&CK techniques

How it is exploited and what it leads to, in MITRE ATT&CK terms.

  • T1133 External Remote Services exploitation
  • T1557 Adversary-in-the-Middle primary impact
  • T1005 Data from Local System secondary impact

kev release 2025-07-28, att&ck v16.1. KEV to ATT&CK mappings by the MITRE Center for Threat-Informed Defense (Mappings Explorer, Apache-2.0). © 2026 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation. Terms of use

CISA SSVC

Exploitation
Active, exploited in the wild
Automatable
no
Technical impact
partial
Assessed
5 y ago

Exploit prediction

18.57% chance of exploitation in the next 30 days, higher than 97% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • Nuclei template FortiOS - Insecure LDAP Configuration Detection nuclei detection template

CVSS scores

assigned by version score vector
CISA ADP 3.1 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 3.1 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CNA 3.1 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 3.3 AV:A/AC:L/Au:N/C:P/I:N/A:N

Affected products

  • Fortinet Fortinet FortiOS

Classification

Weakness
  • CWE-306 Missing Authentication for Critical Functionality
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.