CVE-2023-0811
📋 TL;DR
This vulnerability in Omron CJ1M PLC units allows attackers to overwrite the UM password memory region via PROGRAM AREA WRITE commands. This can disable user memory protections or set non-ASCII passwords, preventing legitimate engineers from accessing or modifying programs. Affects Omron CJ1M units version 4.0 and earlier.
💻 Affected Systems
- Omron CJ1M Programmable Logic Controller (PLC)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete loss of control over industrial processes, unauthorized program modifications leading to equipment damage or safety incidents, and permanent lockout of legitimate engineers.
Likely Case
Unauthorized access to PLC programs, modification of control logic, and denial of service to legitimate engineers through password lockout.
If Mitigated
Limited impact if network segmentation prevents access to PLC programming ports and proper access controls are implemented.
🎯 Exploit Status
Exploitation requires network access to PLC programming port (typically 9600/tcp) and knowledge of specific memory addresses. No authentication is required to send PROGRAM AREA WRITE commands.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 4.1 or later
Vendor Advisory: https://www.ia.omron.com/product/vulnerability/OMSR-2023-001_en.pdf
Restart Required: Yes
Instructions:
1. Download firmware version 4.1 or later from Omron support portal. 2. Connect to CJ1M unit via programming cable. 3. Use CX-Programmer software to upload new firmware. 4. Restart the PLC unit after firmware update completes.
🔧 Temporary Workarounds
Network Segmentation
allIsolate CJ1M PLCs in separate network segments with strict firewall rules preventing unauthorized access to programming ports.
Access Control Lists
allImplement IP-based access control lists on network devices to restrict access to PLC programming ports (typically TCP 9600) to authorized engineering stations only.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate PLCs from untrusted networks
- Deploy industrial firewall with deep packet inspection to block unauthorized PROGRAM AREA WRITE commands
🔍 How to Verify
Check if Vulnerable:
Check firmware version via CX-Programmer software connected to CJ1M unit. Versions 4.0 and earlier are vulnerable.Check Version:
Use CX-Programmer software: Connect to PLC → PLC Information → Check Firmware VersionVerify Fix Applied:
After updating to version 4.1 or later, verify firmware version in CX-Programmer and test that PROGRAM AREA WRITE commands to password memory region are properly rejected.📡 Detection & Monitoring
Log Indicators:
- Unauthorized PROGRAM AREA WRITE commands in PLC logs
- Multiple failed password attempts followed by successful access
Network Indicators:
- PROGRAM AREA WRITE commands to memory address 0x0000-0x000F from unauthorized IP addresses
- Traffic to TCP port 9600 from non-engineering stations
SIEM Query:
source_ip NOT IN (authorized_engineering_ips) AND dest_port=9600 AND payload CONTAINS 'PROGRAM AREA WRITE'