CVE-2019-6816
📋 TL;DR
This vulnerability allows attackers to inject malicious code via Modbus protocol to unauthorizedly modify firmware on Modicon Quantum PLCs, potentially causing denial of service. It affects all Modicon Quantum PLC firmware versions and could impact industrial control systems using these devices.
💻 Affected Systems
- Schneider Electric Modicon Quantum PLCs
📦 What is this software?
Modicon Quantum Firmware by Schneider Electric
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to modify PLC firmware, disrupt industrial processes, cause physical damage, or establish persistent access to critical infrastructure.
Likely Case
Unauthorized firmware modification leading to denial of service, production downtime, or manipulation of industrial processes.
If Mitigated
Limited impact if network segmentation, access controls, and monitoring prevent unauthorized Modbus access.
🎯 Exploit Status
Modbus protocol typically lacks authentication, making exploitation straightforward for attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware updates available per Schneider Electric advisory
Vendor Advisory: https://www.schneider-electric.com/en/download/document/SEVD-2019-134-09/
Restart Required: Yes
Instructions:
1. Download firmware update from Schneider Electric portal. 2. Backup current configuration. 3. Apply firmware update via programming software. 4. Restart PLC. 5. Verify firmware version.
🔧 Temporary Workarounds
Network Segmentation
allIsolate Modbus traffic to trusted networks only
Firewall Rules
allRestrict Modbus TCP (port 502) access to authorized IPs only
🧯 If You Can't Patch
- Implement strict network segmentation to isolate PLCs from untrusted networks
- Deploy industrial firewall with deep packet inspection for Modbus traffic
🔍 How to Verify
Check if Vulnerable:
Check if Modicon Quantum PLC is using Modbus protocol and accessible via networkCheck Version:
Use Schneider Electric programming software to read PLC firmware versionVerify Fix Applied:
Verify firmware version matches patched version from Schneider Electric advisory📡 Detection & Monitoring
Log Indicators:
- Unauthorized Modbus write requests
- Unexpected firmware modification attempts
- Multiple failed Modbus function codes
Network Indicators:
- Modbus TCP traffic from unauthorized sources
- Unusual Modbus function code 15 or 16 (write multiple registers/coils)
- Traffic to port 502 from unexpected IPs
SIEM Query:
source_port=502 AND (function_code=15 OR function_code=16) AND NOT src_ip IN [authorized_ips]