CVE-2019-5591
Published: November 3, 2021
Official Description
Fortinet FortiOS contains a default configuration vulnerability that may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the Lightweight Directory Access Protocol (LDAP) server.
CISA KEV Advisory
Fortinet FortiOS Default Configuration Vulnerability
Fortinet FortiOS contains a default configuration vulnerability that may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the Lightweight Directory Access Protocol (LDAP) server.
Apply updates per vendor instructions.
Risk Analysis
A default configuration vulnerability in Fortinet FortiOS allows an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating an LDAP server. With an EPSS score of 0.51605, there is a high likelihood of exploitation. This vulnerability is in CISA's KEV catalog, indicating active exploitation.
This vulnerability is actively exploited in the wild and is included in CISA's Known Exploited Vulnerabilities catalog. Exploitation requires the attacker to be on the same subnet as the affected device.
Administrators should review and modify default configurations in Fortinet FortiOS to prevent LDAP server impersonation. Implement secure communication protocols and network segmentation to isolate LDAP traffic.
Technical Analysis
CVE-2019-5591 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
CISA has added CVE-2019-5591 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
Affected Vendors & Products
Exploit & PoC Resources
All References (1)
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2019-5591 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1