CVE-2020-20741
📋 TL;DR
This vulnerability allows remote attackers to bypass authentication on Beckhoff CX9020 devices by exploiting improper connection handling in the CE Remote Display Tool. Attackers can gain unauthorized access to the Windows CE system without valid credentials. This affects Beckhoff CX9020 devices with specific firmware versions.
💻 Affected Systems
- Beckhoff Automation GmbH & Co. KG CX9020
📦 What is this software?
Cx9020 by Beckhoff
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the industrial control system allowing attackers to manipulate processes, steal sensitive data, or cause physical damage to industrial equipment.
Likely Case
Unauthorized access to the device leading to configuration changes, data exfiltration, or use as a pivot point into industrial networks.
If Mitigated
Limited impact if device is isolated behind firewalls with strict network segmentation and access controls.
🎯 Exploit Status
The vulnerability is simple to exploit - attackers just need to connect to the service and provide incorrect credentials. The connection remains open despite authentication failure.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Contact Beckhoff for updated firmware
Vendor Advisory: https://download.beckhoff.com/download/Document/product-security/Advisories/advisory-2019-006.pdf
Restart Required: Yes
Instructions:
1. Contact Beckhoff support for updated firmware. 2. Backup current configuration. 3. Apply firmware update following Beckhoff documentation. 4. Restart device. 5. Verify authentication now properly closes connections on failed attempts.
🔧 Temporary Workarounds
Network Segmentation
allIsolate CX9020 devices in separate network segments with strict firewall rules
Disable Remote Display Tool
windowsDisable or restrict access to the CE Remote Display Tool service if not required
🧯 If You Can't Patch
- Implement strict network access controls to limit connections to CX9020 devices
- Monitor all connections to CX9020 devices and alert on authentication failures
🔍 How to Verify
Check if Vulnerable:
Check firmware version matches affected version and test if CE Remote Display Tool maintains connections after failed authenticationCheck Version:
Check device firmware version in Beckhoff TwinCAT System Manager or device web interfaceVerify Fix Applied:
Test authentication with incorrect credentials - connection should be immediately closed📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts from same source without connection termination
- Successful connections without preceding successful authentication logs
Network Indicators:
- Unexpected connections to CE Remote Display Tool port (default 48898)
- Sustained connections after authentication failures
SIEM Query:
source_ip="*" AND destination_port=48898 AND (authentication_result="failure" AND connection_duration>5s)