CVE-2026-51538 in OpENer
Summary
by MITRE • 07/14/2026
EIPStackGroup OpENer 2.3.0 (commit 76b95cf) suffers from an Incorrect Access Control vulnerability in its handling of encapsulation sessions. When the server processes critical encapsulation commands, it verifies whether the provided session_handle exists in the global session list, but it fails to verify whether that handle belongs to the specific TCP connection issuing the request. Because there is no strong binding between a session handle and its originating socket, any attacker on the network can use a valid session handle created by another legitimate client to bypass access controls.
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Analysis
by VulDB Data Team • 07/14/2026
The EIPStackGroup OpENer 2.3.0 implementation contains a critical access control vulnerability that stems from improper session handle validation during encapsulation command processing. This flaw exists in the server's session management logic where the system performs existence checks on session handles but neglects to validate the cryptographic binding between the handle and the originating network connection. The vulnerability manifests when legitimate clients establish encapsulation sessions, creating session handles that are stored in a global session list for later reference. However, the implementation lacks mechanisms to ensure that a session handle can only be used by the TCP connection that originally created it, creating a fundamental security gap in the authorization model.
The technical flaw represents a classic case of improper access control as defined by CWE-284, where the system fails to properly enforce access restrictions on resources. During encapsulation command processing, the server accepts session handles without verifying that they originate from the same TCP connection that issued the request. This allows for session handle reuse attacks where an attacker intercepts a valid session handle from one client and uses it to impersonate that client's identity when making subsequent requests. The vulnerability is particularly dangerous because it operates at the network protocol level, where session handles are treated as globally accessible identifiers rather than connection-bound tokens.
The operational impact of this vulnerability extends beyond simple unauthorized access to encompass potential system compromise and data integrity violations. An attacker who gains knowledge of a valid session handle can bypass authentication mechanisms and execute commands within the scope of the original user's privileges. This includes access to sensitive industrial control functions, configuration changes, and potentially destructive operations that could affect operational technology systems. The vulnerability is especially concerning in industrial environments where OpENer may be used for communication between programmable logic controllers and human machine interfaces, as it creates a pathway for unauthorized system manipulation.
Mitigation strategies should focus on implementing strong session handle binding to originating connections through cryptographic means or connection tracking mechanisms that maintain the association between session identifiers and their source TCP sockets. The implementation should enforce strict validation checks that verify not only handle existence but also proper authorization based on connection context. Organizations should consider implementing additional security layers such as session timeout mechanisms, connection-based access controls, and regular session handle rotation to reduce the window of opportunity for exploitation. Network segmentation and monitoring solutions can also help detect anomalous behavior patterns that might indicate session handle misuse attempts. The vulnerability aligns with ATT&CK technique T1078 which covers valid accounts and legitimate credentials used for unauthorized access, making it particularly relevant in environments where industrial control systems are targeted for lateral movement and privilege escalation attacks.