CVE-2021-20826
📋 TL;DR
This vulnerability allows attackers to intercept credentials transmitted between IDEC PLCs and their management software due to lack of encryption. Affected organizations using vulnerable IDEC PLC hardware and software can have their industrial control systems compromised, potentially leading to operational disruption.
💻 Affected Systems
- FC6A Series MICROSmart All-in-One CPU module
- FC6A Series MICROSmart Plus CPU module
- WindLDR
- WindEDIT Lite
- Data File Manager
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete takeover of PLC operations allowing manipulation of physical outputs, suspension of industrial processes, and potential safety hazards in critical infrastructure.
Likely Case
Unauthorized access to PLC web interface leading to configuration changes, operational data theft, and potential process disruption.
If Mitigated
Limited impact with proper network segmentation and monitoring, though credential exposure still presents risk.
🎯 Exploit Status
Exploitation requires network access to intercept traffic but uses standard network sniffing techniques.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: FC6A All-in-One v2.33+, FC6A Plus v1.92+, WindLDR v8.19.2+, WindEDIT Lite v1.3.2+, Data File Manager v2.12.2+
Vendor Advisory: https://www.idec.com/home/lp/pdf/2021-12-24-PLC.pdf
Restart Required: Yes
Instructions:
1. Download updated firmware/software from IDEC website. 2. Backup PLC configurations. 3. Update PLC firmware via WindLDR. 4. Update all management software. 5. Restart PLC and verify functionality.
🔧 Temporary Workarounds
Network Segmentation
allIsolate PLC network from other networks to limit attack surface
VPN Tunnel
allEstablish encrypted VPN between management stations and PLCs
🧯 If You Can't Patch
- Implement strict network segmentation with firewall rules blocking unnecessary traffic to PLCs
- Deploy network monitoring to detect credential interception attempts and unauthorized access
🔍 How to Verify
Check if Vulnerable:
Check version numbers in WindLDR software and PLC firmware against vulnerable versions listed in advisoryCheck Version:
In WindLDR: Help → About; On PLC: Check firmware version via web interface or programming softwareVerify Fix Applied:
Confirm all software/firmware versions are at or above patched versions, test communication while monitoring network traffic for encrypted credentials📡 Detection & Monitoring
Log Indicators:
- Failed authentication attempts on PLC web interface
- Unusual configuration changes
- Multiple login attempts from new IP addresses
Network Indicators:
- Cleartext credential transmission on port 80/8080 to PLC IPs
- Unusual traffic patterns to PLC management ports
- ARP spoofing or MITM activity in PLC network
SIEM Query:
source_ip="PLC_IP" AND (event_type="authentication" OR event_type="configuration_change") AND result="success" AND user NOT IN ["authorized_users"]