CVE-2018-7846
📋 TL;DR
This vulnerability allows attackers to bypass authentication on Schneider Electric Modicon PLCs via brute force attacks on the Modbus protocol. It affects all versions of Modicon M580, M340, Quantum, and Premium controllers, potentially granting unauthorized access to industrial control systems.
💻 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.
Likely Case
Unauthorized access to PLCs allowing manipulation of industrial processes, data theft, or denial of service.
If Mitigated
Limited impact with proper network segmentation and authentication controls in place.
🎯 Exploit Status
Brute force attacks on Modbus protocol are well-documented and tools are publicly available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Schneider Electric security updates
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. 2. Apply updates following vendor instructions. 3. Restart affected controllers. 4. Verify patch application.
🔧 Temporary Workarounds
Network Segmentation
allIsolate PLCs from untrusted networks using firewalls and VLANs.
Modbus Access Control
allRestrict Modbus protocol access to authorized IP addresses only.
🧯 If You Can't Patch
- Implement strict network segmentation and firewall rules to block unauthorized Modbus access.
- Deploy intrusion detection systems to monitor for brute force attempts on Modbus ports.
🔍 How to Verify
Check if Vulnerable:
Check if affected Schneider Electric PLC models are exposed to Modbus protocol without authentication controls.Check Version:
Use Schneider Electric engineering software to check PLC firmware version.Verify Fix Applied:
Verify firmware version matches patched versions from Schneider Electric advisory.📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts on Modbus ports
- Unusual Modbus traffic patterns
Network Indicators:
- Brute force attempts on TCP port 502 (Modbus)
- Unauthorized IP addresses accessing Modbus services
SIEM Query:
source_port:502 AND (event_type:authentication_failure OR event_count > threshold)