CVE-2018-7843 in Modicon M580
Summary
by MITRE
A CWE-248: Uncaught Exception vulnerability exists in all versions of the Modicon M580, Modicon M340, Modicon Quantum, and Modicon Premium which could cause denial of service when reading memory blocks with an invalid data size or with an invalid data offset in the controller over Modbus.
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Analysis
by VulDB Data Team • 09/23/2023
The vulnerability identified as CVE-2018-7843 represents a critical uncaught exception flaw classified under CWE-248 that affects several Siemens Modicon series controllers including the M580, M340, Quantum, and Premium models. This weakness manifests when these industrial control systems process memory read requests through the Modbus protocol with malformed parameters, specifically invalid data size or invalid data offset values. The affected devices operate within critical infrastructure environments where reliability and continuous operation are paramount, making this vulnerability particularly concerning for operational technology security.
The technical implementation of this vulnerability stems from insufficient error handling within the Modbus communication stack of these controllers. When a Modbus request is received with invalid parameters such as a data size that exceeds available memory boundaries or an offset that references non-existent memory locations, the system fails to properly validate these inputs before attempting memory access operations. This lack of input validation causes the controller's exception handling mechanisms to be bypassed, resulting in abrupt system termination and subsequent denial of service conditions. The flaw operates at the application layer of the communication protocol stack, specifically within the memory management functions that process Modbus read commands.
From an operational impact perspective, this vulnerability creates significant risk for industrial environments relying on these controllers for process automation and control. The denial of service condition can lead to complete system unavailability, potentially causing production halts, safety system failures, or emergency shutdowns in critical manufacturing processes. The vulnerability is particularly dangerous because it can be exploited remotely through Modbus network connections, allowing attackers to disrupt operations without physical access to the equipment. This makes it a prime target for both nation-state actors and cybercriminals seeking to disrupt critical infrastructure operations, with potential impacts ranging from financial losses to safety hazards in industrial environments.
Organizations should implement multiple layers of mitigation strategies to address this vulnerability effectively. Network segmentation and access control measures should be deployed to restrict Modbus traffic to authorized systems only, while implementing network monitoring solutions to detect anomalous Modbus traffic patterns. Device firmware updates from Siemens should be applied immediately to address the root cause of the vulnerability, with thorough testing to ensure compatibility with existing control systems. Additional protective measures include implementing Modbus protocol filtering at network boundaries, deploying intrusion detection systems specifically configured to identify malformed Modbus requests, and establishing robust network access controls through firewalls and access control lists. The vulnerability aligns with ATT&CK technique T1499.001 which involves network denial of service attacks, and represents a significant concern for ICS environments that require high availability and reliability in their control systems.