Resource Exhaustion in OpENer 2.3.0

Executive Summary

This vulnerability exists in OpENer version 2.3.0, specifically in its network processing loop. It is a resource exhaustion issue that can lead to a Denial of Service (DoS).

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Impact Analysis

The vulnerability can cause a Denial of Service by exhausting system resources in the network processing loop of OpENer 2.3.0. This means the affected system may become unresponsive or unavailable.

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Detection Guidance

This vulnerability can be detected by monitoring for unusual or stalled TCP connections on the default ENIP TCP port 44818, especially connections that remain open while sending incomplete Ethernet/IP (ENIP) packets.

A practical approach is to check for TCP connections to port 44818 that have sent partial data and remain in an established state without completing the handshake or data transfer.

• Use netstat or ss to list TCP connections on port 44818 and look for long-lived connections: netstat -an | grep ':44818' | grep ESTABLISHED
• Use tcpdump or Wireshark to capture and analyze traffic on port 44818, looking for incomplete ENIP packets or connections with minimal data sent: tcpdump -i <interface> tcp port 44818
• Monitor system logs or application logs for signs of the network handler blocking or stalling.

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Mitigation Strategies

Immediate mitigation steps include restricting access to the ENIP TCP port 44818 to trusted hosts only, such as internal engineering workstations or PLCs, to reduce exposure to unauthenticated remote attackers.

Implement network-level protections such as firewall rules or intrusion prevention systems to detect and block suspicious connections that send incomplete ENIP packets or exhibit Slowloris-style behavior.

Monitor and limit the number of simultaneous TCP connections to port 44818 to prevent resource exhaustion.

Apply any available patches or updates from the OpENer project that address this vulnerability once they are released.

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Compliance Impact

The provided information does not specify any direct impact of CVE-2026-51535 on compliance with common standards and regulations such as GDPR or HIPAA.

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