CVE-2019-5591

MEDIUM KEV RANSOMWARE NUCLEI

FortiOS < 6.2.0 - Unauthenticated Sensitive Information Interception via LDAP Server Impersonation

Title source: llm
STIX 2.1

Exploitation Summary

CVE-2019-5591 is actively exploited and listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added November 3, 2021, with confirmed use in ransomware campaigns. EIP tracks 1 public exploit from researchers including ayewo. A Nuclei detection template is also available.

AI-analyzed exploit summary This PoC demonstrates a MITM attack against FortiOS LDAP authentication by impersonating an LDAP server to capture credentials. It includes a Python-based LDAP honeypot that logs BIND and SEARCH requests, extracting and exfiltrating credentials.

Description

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

Exploits (1)

nomisec WORKING POC
by ayewo · poc
https://github.com/ayewo/fortios-ldap-mitm-poc-CVE-2019-5591

This PoC demonstrates a MITM attack against FortiOS LDAP authentication by impersonating an LDAP server to capture credentials. It includes a Python-based LDAP honeypot that logs BIND and SEARCH requests, extracting and exfiltrating credentials.

Classification
Working Poc 95%
Attack Type
Auth Bypass
Complexity
Moderate
Reliability
Reliable
Target: FortiOS 6.0.3 through 6.2.0
No auth needed
Prerequisites: Network access to the local subnet of the FortiGate device · Vulnerable FortiOS version
devstral-2 · analyzed Feb 16, 2026 Full analysis →

Nuclei Templates (1)

FortiOS - Insecure LDAP Configuration Detection
MEDIUMby ayewo
Shodan: cpe:"cpe:2.3:o:fortinet:fortios"

References (2)

Core 2
Core References
Mitigation, Vendor Advisory x_refsource_confirm
https://www.fortiguard.com/psirt/FG-IR-19-037

Scores

CVSS v3 6.5
EPSS 0.1857
EPSS Percentile 96.9%
Attack Vector ADJACENT_NETWORK
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CISA SSVC

Vulnrichment
Exploitation active
Automatable no
Technical Impact partial

Details

CISA KEV 2021-11-03
VulnCheck KEV 2021-04-02
InTheWild.io 2021-07-23
ENISA EUVD EUVD-2019-15166
Ransomware Use Confirmed
CWE
CWE-306
Status published
Products (1)
fortinet/fortios < 6.2.0
Published Aug 14, 2020
KEV Added Nov 03, 2021
Tracked Since Feb 18, 2026