CVE-2021-40872
📋 TL;DR
This vulnerability in Softing Industrial Automation uaToolkit Embedded allows remote attackers to cause denial of service (DoS) by crashing the OPC/UA server process or bypass authentication to login as anonymous users. It affects industrial automation systems using affected versions of the uaToolkit Embedded library. The issue stems from an invalid type cast when processing crafted messages.
💻 Affected Systems
- Softing Industrial Automation uaToolkit Embedded
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers gain unauthorized access as anonymous users to industrial control systems, potentially manipulating processes or causing system crashes that disrupt critical operations.
Likely Case
Denial of service attacks that crash OPC/UA servers, requiring manual restart and causing temporary operational disruption in industrial environments.
If Mitigated
Limited impact with proper network segmentation and monitoring, though authentication bypass could still occur if exploited.
🎯 Exploit Status
Exploitation requires sending crafted messages to OPC/UA server endpoints, which are typically exposed on industrial networks.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.40 or later
Vendor Advisory: https://industrial.softing.com/fileadmin/sof-files/pdf/ia/support/Security_Bulletin_CVE-2021-40872.pdf
Restart Required: Yes
Instructions:
1. Download uaToolkit Embedded version 1.40 or later from Softing. 2. Rebuild and redeploy OPC/UA applications with the updated library. 3. Restart all affected OPC/UA server processes.
🔧 Temporary Workarounds
Network Segmentation
allIsolate OPC/UA servers from untrusted networks using firewalls or network segmentation.
Access Control Lists
allRestrict access to OPC/UA server ports (typically 4840/tcp) to authorized systems only.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate OPC/UA servers from untrusted networks
- Deploy intrusion detection systems to monitor for anomalous OPC/UA traffic patterns
🔍 How to Verify
Check if Vulnerable:
Check if OPC/UA server uses uaToolkit Embedded library version earlier than 1.40Check Version:
Check application documentation or contact vendor for version informationVerify Fix Applied:
Verify uaToolkit Embedded library version is 1.40 or later in deployed applications📡 Detection & Monitoring
Log Indicators:
- Unexpected OPC/UA server crashes
- Authentication failures followed by anonymous access
Network Indicators:
- Unusual OPC/UA message patterns to port 4840/tcp
- Multiple connection attempts with malformed packets
SIEM Query:
source_port:4840 AND (event_type:crash OR auth_result:anonymous)