CVE-2021-27498
📋 TL;DR
A denial-of-service vulnerability in EIPStackGroup OpENer EtherNet/IP stack allows attackers to crash affected systems by sending specially crafted packets. This affects industrial control systems and devices using vulnerable versions of the OpENer library. The vulnerability requires network access to the target system.
💻 Affected Systems
- EIPStackGroup OpENer EtherNet/IP stack
📦 What is this software?
Opener by Opener Project
⚠️ Risk & Real-World Impact
Worst Case
Complete system crash requiring manual restart, potentially disrupting industrial processes or critical operations.
Likely Case
Service disruption causing temporary unavailability of EtherNet/IP communication until system restart.
If Mitigated
Minimal impact with proper network segmentation and monitoring detecting malicious packets.
🎯 Exploit Status
Exploitation requires sending crafted packets to the vulnerable service, no authentication needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions from February 10, 2021 onward
Vendor Advisory: https://github.com/EIPStackGroup/OpENer
Restart Required: Yes
Instructions:
1. Update OpENer library to version from Feb 10, 2021 or later. 2. Recompile any applications using the library. 3. Restart affected services or devices.
🔧 Temporary Workarounds
Network Segmentation
allIsolate EtherNet/IP devices from untrusted networks using firewalls or VLANs.
Packet Filtering
allImplement network filtering to block suspicious EtherNet/IP packets at perimeter.
🧯 If You Can't Patch
- Implement strict network access controls to limit who can communicate with EtherNet/IP services.
- Deploy intrusion detection systems to monitor for DoS attempts and anomalous traffic patterns.
🔍 How to Verify
Check if Vulnerable:
Check if OpENer library version predates February 10, 2021 in your application or device.Check Version:
Check application documentation or vendor information for OpENer library version.Verify Fix Applied:
Confirm OpENer library version is from Feb 10, 2021 or later and test service stability.📡 Detection & Monitoring
Log Indicators:
- Unexpected service crashes
- EtherNet/IP service restarts
- Connection resets
Network Indicators:
- Malformed EtherNet/IP packets
- Sudden traffic spikes to EtherNet/IP ports
SIEM Query:
source_port:44818 AND (packet_size:anomalous OR protocol_violation:true)