CVE-2019-6808
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on Schneider Electric Modicon PLCs by exploiting improper access control in Modbus protocol configuration settings. It affects all versions of Modicon M580, M340, Quantum, and Premium controllers. Attackers can overwrite controller configurations without authentication.
💻 Affected Systems
- Modicon M580
- Modicon M340
- Modicon Quantum
- Modicon Premium
📦 What is this software?
Modicon M340 Firmware by Schneider Electric
Modicon M580 Firmware by Schneider Electric
Modicon Premium Firmware by Schneider Electric
Modicon Quantum Firmware by Schneider Electric
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of industrial control systems leading to physical damage, production shutdown, or safety incidents through remote code execution on PLCs.
Likely Case
Unauthorized modification of PLC configurations causing operational disruption, data manipulation, or denial of service in industrial environments.
If Mitigated
Limited impact if controllers are isolated behind firewalls with strict network segmentation and Modbus traffic filtering.
🎯 Exploit Status
Exploitation requires only network access to Modbus ports (typically TCP 502). Public technical details available in Talos advisory.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Schneider Electric security update SEVD-2019-134-11
Vendor Advisory: https://www.schneider-electric.com/en/download/document/SEVD-2019-134-11/
Restart Required: Yes
Instructions:
1. Download firmware updates from Schneider Electric portal. 2. Apply updates following vendor documentation. 3. Restart controllers after patching. 4. Verify configuration integrity.
🔧 Temporary Workarounds
Network Segmentation
allIsolate PLCs in separate network segments with strict firewall rules.
Modbus Port Restriction
linuxBlock external access to Modbus TCP port 502 and restrict internal access.
iptables -A INPUT -p tcp --dport 502 -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation with industrial DMZ architecture
- Deploy intrusion detection systems monitoring Modbus traffic anomalies
🔍 How to Verify
Check if Vulnerable:
Check if Modbus TCP port 502 is accessible and controller models match affected list.Check Version:
Use Schneider Electric engineering software (EcoStruxure Control Expert) to read controller firmware version.Verify Fix Applied:
Verify firmware version against Schneider Electric patched versions and test Modbus access controls.📡 Detection & Monitoring
Log Indicators:
- Unusual Modbus write requests
- Configuration change alerts from PLCs
- Multiple failed authentication attempts on industrial network
Network Indicators:
- Unexpected Modbus traffic to port 502
- Modbus function code 16 (Write Multiple Registers) from unauthorized sources
- Traffic from non-industrial network segments to PLCs
SIEM Query:
source_port:502 AND (function_code:16 OR function_code:06) AND NOT src_ip IN [authorized_plc_ips]