CVE-2021-33485
📋 TL;DR
CVE-2021-33485 is a critical heap-based buffer overflow vulnerability in CODESYS Control Runtime systems. Successful exploitation could allow remote attackers to execute arbitrary code or cause denial of service. Organizations using CODESYS industrial control systems for automation and PLC programming are affected.
💻 Affected Systems
- CODESYS Control Runtime system
📦 What is this software?
Control by Codesys
Control by Codesys
Control by Codesys
Control by Codesys
Control by Codesys
Control by Codesys
Control by Codesys
Control by Codesys
Control by Codesys
Control Rte by Codesys
Control Rte by Codesys
Hmi by Codesys
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, manipulation of industrial processes, or permanent system damage.
Likely Case
Denial of service causing industrial process disruption, with potential for limited code execution in vulnerable configurations.
If Mitigated
Contained impact with proper network segmentation and access controls, potentially limited to denial of service.
🎯 Exploit Status
Heap-based buffer overflow typically requires specific input crafting but CVSS 9.8 suggests relatively straightforward exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.5.17.10 and later
Vendor Advisory: https://customers.codesys.com/index.php?eID=dumpFile&t=f&f=14805&token=f0b86f99bb302ddd4aadec483aed5f5d3fddbf1a&download=
Restart Required: Yes
Instructions:
1. Download CODESYS Control Runtime version 3.5.17.10 or later from CODESYS customer portal. 2. Backup current configuration and programs. 3. Install the updated runtime following vendor instructions. 4. Restart the system. 5. Verify all industrial processes function correctly.
🔧 Temporary Workarounds
Network Segmentation
allIsolate CODESYS systems from untrusted networks and implement strict firewall rules.
Access Control Restrictions
allImplement strict authentication and authorization controls for CODESYS network services.
🧯 If You Can't Patch
- Implement network segmentation to isolate CODESYS systems from other networks
- Deploy intrusion detection systems monitoring for buffer overflow attempts on CODESYS ports
🔍 How to Verify
Check if Vulnerable:
Check CODESYS Control Runtime version via CODESYS IDE or system information tools. Versions below 3.5.17.10 are vulnerable.Check Version:
Check via CODESYS IDE: Project → Target Settings → Device or system-specific version commandsVerify Fix Applied:
Verify installed version is 3.5.17.10 or higher and test industrial processes for proper functionality.📡 Detection & Monitoring
Log Indicators:
- Unexpected process crashes
- Memory access violation errors
- Unusual network connections to CODESYS ports
Network Indicators:
- Unusual traffic patterns to CODESYS default ports (1217, 2455, etc.)
- Buffer overflow patterns in network traffic
SIEM Query:
source="codesys" AND (event_type="crash" OR event_type="memory_violation") OR dest_port IN (1217, 2455) AND payload_size>threshold