CVE-2020-7502
📋 TL;DR
This vulnerability allows remote attackers to cause a Denial of Service (DoS) on Schneider Electric Modicon M218 Logic Controllers by sending specially crafted TCP/IP packets. The out-of-bounds write vulnerability affects firmware versions 4.3 and earlier. Industrial control systems using these PLCs in manufacturing, infrastructure, or building automation are at risk.
💻 Affected Systems
- Schneider Electric Modicon M218 Logic Controller
📦 What is this software?
Modicon M218 Firmware by Schneider Electric
⚠️ Risk & Real-World Impact
Worst Case
Complete controller crash requiring physical reset, disrupting industrial processes and potentially causing production downtime or safety issues in critical infrastructure.
Likely Case
Controller becomes unresponsive, requiring manual reboot and causing temporary disruption to automated processes.
If Mitigated
If network segmentation and firewall rules are properly configured, the attack surface is reduced, though internal threats remain possible.
🎯 Exploit Status
The vulnerability requires sending crafted TCP/IP packets to the controller's network interface. No authentication is required, making exploitation straightforward for attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware version 4.4 or later
Vendor Advisory: https://www.se.com/ww/en/download/document/SEVD-2020-161-01
Restart Required: Yes
Instructions:
1. Download firmware version 4.4 or later from Schneider Electric's website. 2. Connect to the M218 controller via programming software. 3. Backup current program and configuration. 4. Upload and install the new firmware. 5. Restore program and configuration. 6. Verify firmware version and functionality.
🔧 Temporary Workarounds
Network Segmentation
allIsolate M218 controllers in separate network segments with strict firewall rules
Access Control Lists
allImplement ACLs to restrict TCP/IP traffic to only authorized sources
🧯 If You Can't Patch
- Implement strict network segmentation to isolate controllers from untrusted networks
- Deploy intrusion detection systems to monitor for anomalous TCP/IP traffic patterns
🔍 How to Verify
Check if Vulnerable:
Check firmware version via Schneider Electric programming software. If version is 4.3 or earlier, the system is vulnerable.Check Version:
Use Schneider Electric SoMachine or EcoStruxure Machine Expert software to read controller firmware versionVerify Fix Applied:
After patching, verify firmware version shows 4.4 or later in the programming software and confirm normal controller operation.📡 Detection & Monitoring
Log Indicators:
- Controller restart logs
- Network communication errors
- Unexpected TCP/IP connection attempts
Network Indicators:
- Unusual TCP packet patterns to controller IP
- Multiple connection attempts from single source
- Malformed TCP/IP packets
SIEM Query:
source_ip="controller_ip" AND (tcp_flags="malformed" OR packet_size>normal_range)