CVE-2021-41028
📋 TL;DR
This vulnerability allows an unauthenticated attacker on the same network to perform a man-in-the-middle attack between FortiClientEMS and FortiClient endpoints via the telemetry protocol, potentially intercepting or manipulating sensitive data. It affects FortiClientEMS and FortiClient (Windows, Linux, Mac) versions 7.0.1 and below, and 6.4.6 and below.
💻 Affected Systems
- FortiClientEMS
- FortiClientWindows
- FortiClientLinux
- FortiClientMac
📦 What is this software?
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient by Fortinet
Forticlient Endpoint Management Server by Fortinet
View all CVEs affecting Forticlient Endpoint Management Server →
Forticlient Endpoint Management Server by Fortinet
View all CVEs affecting Forticlient Endpoint Management Server →
⚠️ Risk & Real-World Impact
Worst Case
An attacker could intercept and decrypt telemetry data, inject malicious commands, or impersonate the EMS to compromise endpoints, leading to data theft or further network exploitation.
Likely Case
Interception of sensitive telemetry data, such as device information or security logs, enabling reconnaissance or data leakage.
If Mitigated
Limited impact if network segmentation isolates EMS and clients from untrusted networks, reducing the attack surface.
🎯 Exploit Status
Exploitation requires network access and knowledge of the telemetry protocol, but no authentication is needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: FortiClientEMS 7.0.2 or 6.4.7, FortiClient 7.0.2 or 6.4.7
Vendor Advisory: https://fortiguard.com/advisory/FG-IR-21-075
Restart Required: Yes
Instructions:
1. Download the updated version from the Fortinet support portal. 2. Install the patch on FortiClientEMS and all FortiClient endpoints. 3. Restart the EMS service and affected endpoints to apply changes.
🔧 Temporary Workarounds
Network Segmentation
allIsolate FortiClientEMS and FortiClient endpoints from untrusted networks to prevent adjacent attackers from accessing the telemetry protocol.
🧯 If You Can't Patch
- Implement strict network access controls to limit communication between EMS and clients to trusted IPs only.
- Monitor network traffic for unusual patterns or unauthorized connections to the telemetry protocol.
🔍 How to Verify
Check if Vulnerable:
Check the version of FortiClientEMS and FortiClient; if it is 7.0.1 or below, or 6.4.6 or below, the system is vulnerable.Check Version:
On FortiClientEMS: Use the web interface or CLI to check version. On FortiClient: Open the client interface or run 'FortiClient.exe --version' on Windows, or check the About section on Linux/Mac.Verify Fix Applied:
After patching, confirm the version is 7.0.2 or 6.4.7 or higher, and test telemetry communication for secure connections.📡 Detection & Monitoring
Log Indicators:
- Unusual telemetry protocol errors or connection failures in EMS logs
- Suspicious network connections from unknown IPs to EMS telemetry ports
Network Indicators:
- Unexpected traffic on telemetry protocol ports (default 8013/TCP)
- Man-in-the-middle attack signatures in network monitoring tools
SIEM Query:
Example: 'source_ip NOT IN trusted_ips AND dest_port=8013' to detect unauthorized access attempts.