CVE-2026-51537 in OpENer
Summary
by MITRE • 07/14/2026
EIPStackGroup OpENer 2.3.0 (commit 76b95cf) has an out-of-bounds read issue in Connection Manager handling of ForwardOpen requests when processing short malformed packets. An attacker can send a valid ENIP outer frame carrying a malformed CIP ForwardOpen/LargeForwardOpen request, causing the parser to continue reading fields even when request data is insufficient. This issue is remotely triggerable via network traffic and does not require authentication.
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Analysis
by VulDB Data Team • 07/14/2026
The EIPStackGroup OpENer 2.3.0 industrial protocol stack contains a critical out-of-bounds read vulnerability that affects the Connection Manager component during ForwardOpen request processing. This vulnerability stems from inadequate input validation within the CIP (Common Industrial Protocol) parsing logic, specifically when handling malformed ENIP (Ethernet/IP) packets. The flaw manifests when the parser attempts to process ForwardOpen or LargeForwardOpen requests that contain insufficient data fields, leading to unauthorized memory access patterns that extend beyond the allocated buffer boundaries.
The technical implementation of this vulnerability resides in the packet parsing routines where the Connection Manager fails to properly verify the minimum required field lengths before attempting to read subsequent data segments. When an attacker crafts a valid ENIP outer frame containing a malformed CIP ForwardOpen/LargeForwardOpen request, the parser continues executing its reading logic without proper bounds checking. This allows the application to access memory locations beyond the actual packet data, potentially reading uninitialized memory, stack contents, or other sensitive data from adjacent memory regions.
This vulnerability presents significant operational risks within industrial control systems as it is remotely exploitable without requiring any authentication credentials. The attack surface encompasses all devices running OpENer 2.3.0 that are accessible over the network and configured to accept ENIP traffic. The remote trigger capability means that attackers can exploit this issue from outside the facility perimeter, potentially gaining access to internal control system communications and sensitive operational data. Network-based attacks can be executed through standard TCP/IP traffic, making detection and prevention challenging within industrial environments where security monitoring may be limited.
The impact of this vulnerability extends beyond simple information disclosure as it could potentially enable more sophisticated attacks by providing attackers with memory layout insights that might aid in exploitation of additional vulnerabilities. From a cybersecurity perspective, this issue aligns with CWE-129 and CWE-787 which address improper input validation and out-of-bounds read conditions respectively. The vulnerability also maps to ATT&CK technique T1059.005 (Command and Scripting Interpreter: Visual Basic) and T1566.001 (Phishing: Spearphishing Attachment) in scenarios where attackers might leverage memory disclosure for further exploitation phases. Organizations should immediately implement network segmentation controls, firewall rules to restrict ENIP traffic, and deploy IDS/IPS signatures targeting known patterns of this attack vector while planning urgent firmware updates to address the root cause through proper bounds checking implementation.
The vulnerability represents a fundamental flaw in input validation that violates security best practices for industrial protocol implementations. Proper mitigation requires not only patching the specific parsing logic but also implementing comprehensive monitoring for anomalous ENIP traffic patterns and establishing network access controls that limit exposure to trusted networks only. This issue highlights the critical importance of proper memory management and bounds checking in industrial communication stacks, particularly when these systems are exposed to untrusted network environments where authentication is not enforced.