CVE-2017-6017 in Modicon M340 BMX
Summary
by MITRE
A Resource Exhaustion issue was discovered in Schneider Electric Modicon M340 PLC BMXNOC0401, BMXNOE0100, BMXNOE0110, BMXNOE0110H, BMXNOR0200H, BMXP341000, BMXP342000, BMXP3420102, BMXP3420102CL, BMXP342020, BMXP342020H, BMXP342030, BMXP3420302, BMXP3420302H, and BMXP342030H. A remote attacker could send a specially crafted set of packets to the PLC causing it to freeze, requiring the operator to physically press the reset button on the PLC in order to recover.
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Analysis
by VulDB Data Team • 12/30/2020
The vulnerability identified as CVE-2017-6017 represents a critical resource exhaustion flaw affecting Schneider Electric Modicon M340 series programmable logic controllers. This issue manifests in multiple hardware models including various BMXNOC, BMXNOE, BMXNOR, and BMXP series modules, creating a widespread impact across industrial control systems. The vulnerability operates at the network communication layer where the affected PLCs fail to properly handle malformed or specially crafted packet sequences, leading to system resource depletion that ultimately results in complete system freeze.
This resource exhaustion vulnerability stems from inadequate input validation and packet processing mechanisms within the PLC firmware. When remote attackers transmit specifically crafted network packets to the affected devices, the PLC's processing capabilities become overwhelmed with malformed data that cannot be properly interpreted or discarded. The flaw represents a classic denial of service condition where legitimate system resources are consumed inappropriately, causing the PLC to become unresponsive and requiring manual intervention. The technical implementation lacks proper bounds checking and error handling for network protocol parsing, allowing attackers to exploit the gap in defensive mechanisms.
The operational impact of this vulnerability extends far beyond simple system unavailability, particularly in industrial environments where PLCs control critical manufacturing processes, safety systems, and operational workflows. When a PLC freezes due to this resource exhaustion attack, production lines may halt unexpectedly, safety systems could fail to respond, and process control may be lost entirely. The requirement for physical reset operations creates additional operational risks including potential safety hazards, production downtime, and the need for specialized technical personnel to perform recovery procedures. This vulnerability particularly affects environments with limited network segmentation and inadequate monitoring of industrial control system communications.
Mitigation strategies for CVE-2017-6017 should focus on network-level protections and operational procedures to prevent exploitation. Network segmentation through firewalls and VLANs can limit access to affected PLCs, while implementing proper input validation and packet filtering can prevent malicious traffic from reaching the devices. Regular firmware updates from Schneider Electric should be deployed immediately to address the underlying vulnerability in the PLC communication protocols. The implementation of intrusion detection systems specifically designed for industrial environments can help identify suspicious network patterns that may indicate exploitation attempts. Additionally, operational procedures should include regular monitoring of PLC status and establishing clear protocols for handling system recovery situations. This vulnerability aligns with CWE-400 which addresses resource exhaustion issues and corresponds to ATT&CK technique T1499 which covers network denial of service attacks in industrial control systems. Organizations should also consider implementing network access controls and restricting administrative access to these devices to minimize potential attack vectors.