CVE-2017-6034
📋 TL;DR
CVE-2017-6034 is an authentication bypass vulnerability in Schneider Electric Modicon Modbus Protocol where sensitive commands are transmitted in cleartext, allowing attackers to capture and replay commands like run, stop, upload, and download. This affects industrial control systems using vulnerable Schneider Electric Modicon PLCs and related devices, potentially allowing unauthorized control of critical industrial processes.
💻 Affected Systems
- Schneider Electric Modicon PLCs
- Modicon M340
- Modicon M580
- Modicon Quantum
- Modicon Premium
- Other Schneider Electric devices using Modbus protocol
📦 What is this software?
Modbus Firmware by Schneider Electric
⚠️ Risk & Real-World Impact
Worst Case
Complete takeover of industrial control systems leading to physical damage, production shutdowns, or safety incidents by replaying commands to manipulate PLC operations.
Likely Case
Unauthorized control of industrial equipment causing operational disruption, data theft, or manipulation of industrial processes.
If Mitigated
Limited impact if proper network segmentation and encryption controls prevent attackers from accessing Modbus traffic.
🎯 Exploit Status
Exploitation requires network access to capture Modbus traffic. Attack tools for Modbus protocol manipulation are publicly available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Various firmware updates released in 2017 (check specific product documentation)
Vendor Advisory: https://ics-cert.us-cert.gov/advisories/ICSA-17-101-01
Restart Required: Yes
Instructions:
1. Identify affected Schneider Electric Modicon devices. 2. Check Schneider Electric security advisory for specific firmware updates. 3. Apply firmware updates following vendor instructions. 4. Restart devices as required. 5. Verify updates are properly installed.
🔧 Temporary Workarounds
Network Segmentation
allIsolate Modbus traffic to separate VLANs or networks to prevent unauthorized access.
Encryption Implementation
allImplement VPN or encryption for Modbus communications to prevent cleartext capture.
🧯 If You Can't Patch
- Implement strict network access controls to limit who can communicate with Modbus devices
- Deploy network monitoring and intrusion detection specifically for Modbus protocol anomalies
🔍 How to Verify
Check if Vulnerable:
Check device firmware version against Schneider Electric security advisory. Use network monitoring to detect cleartext Modbus traffic.Check Version:
Check through Schneider Electric programming software or device web interface (varies by product)Verify Fix Applied:
Verify firmware version has been updated to patched version. Test that Modbus communications are now encrypted or properly authenticated.📡 Detection & Monitoring
Log Indicators:
- Unauthorized Modbus command attempts
- Multiple failed authentication attempts on industrial devices
- Unusual command patterns (e.g., rapid run/stop commands)
Network Indicators:
- Cleartext Modbus traffic on unexpected network segments
- Modbus traffic from unauthorized IP addresses
- Repeated identical Modbus command sequences
SIEM Query:
source="modbus_traffic" AND (command="run" OR command="stop" OR command="upload" OR command="download") AND NOT src_ip IN allowed_ips