FortiClient EMS Under Fire: Critical CVE-2026-21643 Exploited in Real-World Attacks

A critical SQL injection vulnerability, CVE-2026-21643, has been identified in FortiClient Endpoint Management Server (EMS), a centralized management platform for FortiClient endpoint agents across multiple environments.

The vulnerability is currently under active exploitation in the wild, even though it is not yet listed in major exploited vulnerability catalogs. Early attack activity indicates that threat actors are already targeting exposed systems.

This issue poses a serious risk to organizations that have their FortiClient EMS administrative interface accessible over the internet, as it allows remote compromise without authentication.

• CVE-ID: CVE-2026-21643
• CVSS Score: 9.8 (Critical) 
• EPSS Score: 0.05%
• Vulnerability: SQL Injection vulnerability 
• Affected Product: Fortinet FortiClientEMS

CVE-2026-21643 is caused by improper neutralization of special elements in SQL commands, resulting in a SQL injection vulnerability.

The flaw was introduced in FortiClient EMS during changes to the middleware and database connection layer to support enhanced multi-tenant functionality.

Specifically, an HTTP header used to identify tenant context is passed directly into a backend SQL query without proper sanitization, and this occurs before authentication is enforced.

This vulnerability allows remote, unauthenticated attackers to:

• Execute arbitrary SQL queries on the backend PostgreSQL database
• Access highly sensitive information, including:
  
• Administrative credentials
• Endpoint inventory data
• Security policies
• Certificates for managed endpoints
• Potentially execute unauthorized commands or code on the server

Due to the absence of authentication requirements and the sensitivity of exposed data, the impact is considered critical.

The exploitation process is simple and highly effective:

1. The attacker connects to the FortiClient EMS web interface over HTTPS
2. A specially crafted HTTP request is sent to the server
3. The request contains a malicious tenant-identification HTTP header
4. This header is directly incorporated into a SQL query without validation
5. The injected SQL is executed by the database

To reduce the risk of exploitation of CVE-2026-21643 in Fortinet FortiClient EMS, organizations should take immediate action:

• Update FortiClient EMS from version 7.4.4 to 7.4.5 or later, where the vulnerability has been fixed.
• Limit exposure of the EMS administrative interface by:
  
• Removing public internet access
• Allowing access only via VPN or trusted internal networks

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