CVE-2026-51541 in OpENer
Summary
by MITRE • 07/14/2026
OpENer 2.3.0 (commit 76b95cf) has an out-of-bounds read issue in CIP message parsing when handling malformed explicit requests with a forged EPath size. An attacker can send a valid ENIP SendRRData frame carrying a very short CIP payload whose path_size field claims that many more path words are present than are actually available. Because the parser trusts the attacker-controlled path_size and continues decoding path segments without a remaining-length boundary, it reads beyond the end of the stack receive buffer.
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Analysis
by VulDB Data Team • 07/14/2026
The vulnerability in OpENer 2.3.0 represents a critical out-of-bounds read flaw that arises during CIP message parsing when processing malformed explicit requests with forged EPath sizes. This issue stems from insufficient input validation and boundary checking within the network protocol implementation, specifically affecting the handling of ENIP SendRRData frames containing truncated CIP payloads. The vulnerability manifests when an attacker crafts a malicious frame where the path_size field contains an inflated value that exceeds the actual available data in the receive buffer, creating a scenario where the parser blindly trusts attacker-controlled metadata without proper validation.
The technical execution of this vulnerability occurs through the manipulation of the EPath size field within CIP explicit requests, which directly influences how the parser allocates and reads memory segments during message processing. When the parser encounters a forged path_size value, it proceeds to decode path segments based on this attacker-controlled parameter without verifying whether sufficient data remains in the buffer to satisfy the claimed path length. This fundamental flaw allows the parser to read beyond the legitimate bounds of the stack receive buffer, potentially accessing uninitialized memory regions or data belonging to adjacent memory structures.
This vulnerability presents significant operational risks within industrial control systems and automation environments where OpENer is deployed, as it could enable attackers to extract sensitive information from memory, potentially revealing system configurations, credentials, or other confidential data. The out-of-bounds read may also provide a foundation for more sophisticated attacks including arbitrary code execution or denial of service conditions that could disrupt critical industrial processes. The impact extends beyond simple information disclosure since the parser behavior can be manipulated to access memory locations that might contain pointers, function addresses, or other structured data that could aid in further exploitation attempts.
The vulnerability aligns with CWE-129 and CWE-787 categories from the Common Weakness Enumeration taxonomy, specifically covering improper input validation and out-of-bounds read conditions. From an ATT&CK framework perspective, this weakness maps to techniques involving input validation evasion and memory corruption exploitation, potentially enabling adversaries to move laterally within industrial networks or disrupt operational technology systems. The vulnerability also intersects with ATT&CK technique T1059 for command injection and T1498 for network denial of service, depending on the specific exploitation vector employed by threat actors. Organizations should implement immediate mitigations including input validation enforcement, buffer boundary checking, and limiting the maximum allowable path size values in CIP message processing to prevent exploitation.
Mitigation strategies should focus on strengthening input validation mechanisms within the CIP parser implementation, particularly around EPath size fields and associated path segment decoding routines. The most effective approach involves implementing strict boundary checks that verify whether claimed path lengths are consistent with available buffer space before proceeding with data parsing operations. Additionally, organizations should consider deploying network segmentation controls, implementing intrusion detection systems capable of identifying malformed ENIP frames, and applying firmware updates or patches as soon as they become available from the vendor to address this vulnerability in production environments.