CVE-2021-27478
📋 TL;DR
CVE-2021-27478 is a denial-of-service vulnerability in EIPStackGroup OpENer EtherNet/IP stack where specially crafted network packets can crash the service. This affects industrial control systems and devices using vulnerable versions of the OpENer stack. Attackers can disrupt EtherNet/IP communications by sending malicious packets to vulnerable implementations.
💻 Affected Systems
- EIPStackGroup OpENer EtherNet/IP stack
- Devices and applications incorporating vulnerable OpENer library
📦 What is this software?
Opener by Opener Project
⚠️ Risk & Real-World Impact
Worst Case
Complete disruption of EtherNet/IP communications in industrial environments, potentially halting production processes or safety systems that rely on this protocol.
Likely Case
Service crashes requiring manual restart of affected devices or applications, causing temporary operational disruption.
If Mitigated
Minimal impact with proper network segmentation and monitoring; affected systems automatically restart or failover to redundant components.
🎯 Exploit Status
Exploitation requires sending crafted packets to EtherNet/IP ports (typically TCP/44818, UDP/2222). The vulnerability is in packet parsing logic.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Commit 407f2f3 and later (Feb 10, 2021)
Vendor Advisory: https://github.com/EIPStackGroup/OpENer/commit/407f2f3
Restart Required: Yes
Instructions:
1. Update OpENer library to commit 407f2f3 or later. 2. Recompile applications using the updated library. 3. Restart affected services or devices. 4. For embedded devices, contact manufacturer for firmware updates.
🔧 Temporary Workarounds
Network Segmentation
allIsolate EtherNet/IP devices in separate network segments with strict firewall rules
Port Restriction
allBlock unnecessary access to EtherNet/IP ports (TCP/44818, UDP/2222) from untrusted networks
🧯 If You Can't Patch
- Implement strict network access controls to limit which systems can communicate with EtherNet/IP devices
- Deploy network intrusion detection systems to monitor for malicious EtherNet/IP traffic patterns
🔍 How to Verify
Check if Vulnerable:
Check OpENer library version or commit hash. If using embedded devices, check manufacturer advisories.Check Version:
For source builds: git log --oneline | head -1. For binaries: check with vendor-specific commands.Verify Fix Applied:
Verify OpENer version is commit 407f2f3 or later. Test with known safe packet sequences.📡 Detection & Monitoring
Log Indicators:
- Unexpected service restarts
- Crash logs from OpENer processes
- Connection resets on EtherNet/IP ports
Network Indicators:
- Malformed EtherNet/IP packets
- Unusual traffic patterns to port 44818
- Multiple connection attempts with crafted packets
SIEM Query:
source="firewall" dest_port=44818 AND (packet_size<50 OR packet_size>1500) OR source="syslog" message="*OpENer*crash*"