CVE-2026-75352 in OpENer
Summary
by MITRE • 10/09/2026
OpENer v2.3/commit 76b95cf, contains an integer underflow in the server-side EtherNet/IP ForwardOpen connection-path parser. This allows a remote attacker to cause a denial of service
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Analysis
by VulDB Data Team • 10/09/2026
The vulnerability identified in OpENer versions prior to commit 76b95cf represents a critical security flaw within the implementation of the EtherNet/IP protocol stack, specifically affecting the server-side parsing logic for ForwardOpen connection requests. As an open-source reference implementation widely used by developers and manufacturers to integrate industrial devices with Ethernet networks, OpENer serves as a foundational component in many Industrial Internet of Things (IIoT) deployments. The specific defect resides in how the software processes the connection-path field contained within EtherNet/IP packets during the establishment of explicit messaging connections. This parsing routine fails to adequately validate input data types and ranges before performing arithmetic operations, leading directly to an integer underflow condition when maliciously crafted packet headers are received from a remote attacker.
From a technical perspective, the root cause is classified as CWE-192, which denotes Integer Coercion Error, specifically manifesting as an unsigned integer being treated in a way that allows negative values or unexpected wrap-around behavior during subtraction operations. When a ForwardOpen message arrives with a specially constructed connection path length or identifier field, the parser may subtract a larger value from a smaller one without proper bounds checking. Because C and similar systems programming languages do not always enforce strict type safety at runtime for these low-level structures, this arithmetic error results in an extremely large positive integer due to two's complement representation rules. This erroneous calculation subsequently influences memory allocation routines or buffer indexing logic that rely on the result of this computation.
The operational impact of this vulnerability is severe and primarily centers around availability degradation through denial of service conditions. The miscalculated value derived from the underflow typically triggers an out-of-bounds access, a heap overflow, or causes the application to enter an infinite loop while attempting to process invalid memory addresses. In most practical scenarios involving network daemons like OpENer, this results in immediate segmentation faults and crashes of the service process. For industrial environments where continuous monitoring and control are required, such instability can lead to unplanned downtime, loss of visibility into critical infrastructure assets, and potential cascading failures if redundant systems fail to take over seamlessly. While direct code execution is theoretically possible depending on memory layout exploitation techniques, the primary documented risk remains the disruption of service availability for connected devices relying on this stack.
This vulnerability aligns with MITRE ATT&CK technique T1498, Network Denial of Service, as it enables an attacker to disrupt normal operations by exhausting system resources or crashing services remotely without authentication. It also reflects weaknesses associated with CWE-20, Improper Input Validation, and CWE-787, Out-of-bounds Write, depending on the specific memory state at the time of exploitation. The lack of robust input sanitization in legacy industrial protocols like EtherNet/IP exacerbates these risks, as many devices assume a trusted network environment that is increasingly compromised by modern cyber threats.
Mitigation strategies must prioritize immediate patching to the latest stable version of OpENer where this commit has been integrated and reviewed for security correctness. Developers should implement strict input validation checks before any arithmetic operations involving packet header fields are performed, ensuring that all values fall within expected positive ranges consistent with the EtherNet/IP specification. Additionally, deploying network segmentation policies can limit exposure by restricting access to devices running vulnerable versions of OpENer to only authorized management subnets. Utilizing intrusion detection systems configured to flag anomalous EtherNet/IP traffic patterns may also provide an additional layer of defense against exploitation attempts while remediation efforts are underway.