CVE-2021-22800
📋 TL;DR
CVE-2021-22800 is an input validation vulnerability in Schneider Electric Modicon M218 Logic Controllers that allows remote attackers to cause denial of service by sending specially crafted packets to TCP port 1105. This affects industrial control systems using vulnerable controller versions. Organizations using these controllers in industrial environments 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 failure requiring physical reset or replacement, disrupting industrial processes and causing production downtime.
Likely Case
Controller becomes unresponsive, requiring manual restart and causing temporary process interruption.
If Mitigated
No impact if controllers are properly segmented and protected from untrusted networks.
🎯 Exploit Status
Exploitation requires network access to port 1105/TCP but no authentication. Crafted packet structure is not publicly documented.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: V5.1.0.7 or later
Vendor Advisory: https://download.schneider-electric.com/files?p_Doc_Ref=SEVD-2021-285-04
Restart Required: Yes
Instructions:
1. Download firmware update from Schneider Electric website. 2. Backup controller configuration. 3. Apply firmware update using EcoStruxure Machine Expert software. 4. Restart controller. 5. Restore configuration if needed.
🔧 Temporary Workarounds
Network Segmentation
allIsolate Modicon controllers from untrusted networks using firewalls or network segmentation.
Port Blocking
allBlock access to TCP port 1105 from untrusted networks using firewall rules.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate controllers from untrusted networks
- Deploy industrial firewall rules to block all traffic to port 1105 except from authorized management stations
🔍 How to Verify
Check if Vulnerable:
Check controller firmware version in EcoStruxure Machine Expert software or via web interface if enabled.Check Version:
Use EcoStruxure Machine Expert: Connect to controller and check firmware version in device properties.Verify Fix Applied:
Verify firmware version is V5.1.0.7 or later after update.📡 Detection & Monitoring
Log Indicators:
- Controller restart logs
- Network connection attempts to port 1105
- Controller communication failures
Network Indicators:
- Unusual traffic patterns to port 1105/TCP
- Multiple connection attempts from single source
SIEM Query:
source_port=1105 AND (protocol=TCP) AND (destination_ip=[controller_ip])