CVE-2018-7846 in Modicon M580
Summary
by MITRE
A CWE-501: Trust Boundary Violation vulnerability on connection to the Controller exists in all versions of the Modicon M580, Modicon M340, Modicon Quantum and Modicon Premium which could cause unauthorized access by conducting a brute force attack on Modbus protocol to the controller.
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Analysis
by VulDB Data Team • 09/23/2023
The CVE-2018-7846 vulnerability represents a critical trust boundary violation affecting several legacy industrial control systems manufactured by Schneider Electric. This vulnerability specifically impacts the Modicon M580, Modicon M340, Modicon Quantum, and Modicon Premium series controllers, which are widely deployed in industrial environments for process control and automation. The flaw resides in the controllers' handling of Modbus protocol connections, where the system fails to properly enforce authentication boundaries, creating a pathway for unauthorized access through brute force attack vectors. The vulnerability stems from inadequate session management and authentication mechanisms that allow attackers to repeatedly attempt connection attempts without effective rate limiting or account lockout procedures. This weakness directly maps to CWE-501, which defines trust boundary violations as conditions where the system fails to properly separate trusted and untrusted data flows, leading to potential privilege escalation and unauthorized system access.
The technical implementation of this vulnerability allows attackers to exploit the Modbus protocol's inherent design characteristics to conduct systematic brute force attacks against controller authentication mechanisms. The Modbus protocol, while widely used in industrial environments, lacks robust built-in security features that would prevent such attacks from succeeding. Attackers can leverage this vulnerability to gain unauthorized access to industrial control systems by systematically testing credentials against the affected controllers. The vulnerability is particularly concerning because it affects multiple generations of Schneider Electric controllers, suggesting a widespread exposure across industrial installations. The attack surface is further expanded due to the protocol's simplicity and the common practice of using default credentials or weak passwords in industrial environments. This creates a scenario where attackers can potentially gain full administrative access to critical industrial processes, leading to potential operational disruption, data compromise, or even physical safety risks.
The operational impact of CVE-2018-7846 extends beyond simple unauthorized access to encompass broader industrial control system security implications. When exploited, this vulnerability can enable attackers to manipulate industrial processes, modify control parameters, or gain persistent access to critical infrastructure. The affected controllers are often deployed in environments where operational technology (OT) systems interface directly with physical processes, making unauthorized access potentially dangerous. The vulnerability's exploitation can lead to cascading effects throughout industrial operations, as attackers may use the compromised controllers as entry points to target other connected systems within the industrial network. This creates a significant risk for organizations following ATT&CK framework's initial access and persistence tactics, where the vulnerability serves as a gateway for more sophisticated attacks. The impact is particularly severe in critical infrastructure sectors such as power generation, water treatment, and manufacturing, where the compromise of control systems can have far-reaching consequences.
Mitigation strategies for CVE-2018-7846 should focus on implementing multiple layers of defense to address the trust boundary violation. Organizations should immediately implement strong authentication measures including the use of complex passwords, account lockout mechanisms, and multi-factor authentication where possible. Network segmentation should be implemented to isolate industrial control systems from general corporate networks, reducing the attack surface available to potential adversaries. The implementation of Modbus protocol filtering and monitoring can help detect and prevent brute force attempts against controller interfaces. Organizations should also consider deploying intrusion detection systems specifically designed for industrial environments to monitor for suspicious Modbus traffic patterns. Regular security assessments and vulnerability scanning should be conducted to identify and remediate similar weaknesses across industrial control system deployments. The affected Schneider Electric controllers should be updated with available firmware patches, and organizations should develop incident response procedures specifically addressing industrial control system compromises. Additionally, implementing network access control lists and disabling unnecessary Modbus services can significantly reduce the risk of exploitation, aligning with cybersecurity frameworks that emphasize defense in depth and least privilege access principles.