CVE-2018-7856 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 a possible denial of Service when writing invalid memory blocks to the controller over Modbus.
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Analysis
by VulDB Data Team • 09/23/2023
The vulnerability identified as CVE-2018-7856 represents a critical uncaught exception flaw classified under CWE-248 that affects several legacy industrial control systems including the Modicon M580, M340, Quantum, and Premium series. This vulnerability manifests when these controllers receive invalid memory block write operations through the Modbus protocol, creating a scenario where the system fails to properly handle exceptional conditions and instead crashes or becomes unresponsive. The Modbus protocol serves as a fundamental communication standard in industrial automation environments, making this vulnerability particularly concerning for operational technology infrastructure.
The technical implementation of this vulnerability stems from the controllers' failure to implement proper exception handling mechanisms when processing memory write requests. When an invalid memory block is written to these controllers over Modbus, the system does not gracefully manage the error condition but rather allows the unhandled exception to propagate, resulting in system instability. This behavior aligns with CWE-248's definition of uncaught exceptions where programs fail to handle specific error conditions that occur during execution, leading to unexpected termination or system state corruption. The vulnerability affects all versions of the affected Modicon controllers, indicating a fundamental design flaw rather than a specific software bug that could be patched through targeted updates.
The operational impact of CVE-2018-7856 extends beyond simple system disruption to potentially compromise entire industrial processes that depend on these controllers. A denial of service condition can halt production lines, disrupt critical infrastructure operations, and create safety hazards in environments where continuous operation is essential. The vulnerability's exploitation requires only network access to the Modbus communication channel, making it accessible to attackers who may have gained physical or remote access to the industrial network. This weakness creates opportunities for attackers to leverage the vulnerability for broader attacks within the industrial control system environment, potentially leading to more severe consequences through cascading failures or as part of larger attack campaigns.
Organizations should implement immediate mitigation strategies including network segmentation to isolate critical industrial control systems from general enterprise networks, implementing Modbus protocol filtering and monitoring to detect anomalous memory write operations, and establishing robust network access controls to limit who can communicate with these controllers. The vulnerability's presence in legacy systems highlights the importance of industrial cybersecurity frameworks and the need for comprehensive vulnerability management programs that account for the unique characteristics of operational technology environments. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving service stoppage and system denial of service, potentially enabling adversaries to progress through stages of compromise by creating conditions that facilitate further exploitation. Regular security assessments and network monitoring should be implemented to detect potential exploitation attempts, while system administrators should consider implementing redundant control systems or fail-safe mechanisms to maintain operational continuity during potential attack scenarios.