CVE-2018-7759 in Modicon M340
Summary
by MITRE
A buffer overflow vulnerability exists in Schneider Electric's Modicon M340, Modicon Premium, Modicon Quantum PLC, BMXNOR0200. The buffer overflow vulnerability is caused by the length of the source string specified (instead of the buffer size) as the number of bytes to be copied.
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Analysis
by VulDB Data Team • 01/27/2020
The buffer overflow vulnerability identified in CVE-2018-7759 represents a critical security flaw affecting Schneider Electric's Modicon M340, Modicon Premium, Modicon Quantum PLC, and BMXNOR0200 devices. This vulnerability stems from improper input validation within the system's memory management mechanisms, specifically in how string copy operations are handled. The flaw manifests when the system processes data streams containing maliciously crafted input that exceeds the expected buffer boundaries. The root cause lies in the implementation where the length of the source string is incorrectly used as the parameter for the number of bytes to be copied, rather than the actual buffer size available for the operation.
This technical implementation error creates a scenario where an attacker can manipulate input data to overwrite adjacent memory locations, potentially leading to arbitrary code execution or system instability. The vulnerability operates at the application layer and affects industrial control systems that rely on these programmable logic controllers for critical operations. When exploited, the buffer overflow can result in denial of service conditions, system crashes, or unauthorized access to sensitive operational data. The flaw is particularly concerning in industrial environments where these devices operate as part of critical infrastructure, as it could potentially disrupt manufacturing processes or compromise safety systems.
The operational impact of this vulnerability extends beyond simple system crashes, as it presents a potential pathway for attackers to gain deeper access to industrial control networks. Attackers could leverage this flaw to inject malicious code into the PLC memory, potentially altering control logic or creating backdoor access points. The vulnerability's exploitation requires minimal privileges and can be executed through network-based attacks targeting the affected devices. This makes it particularly dangerous in environments where these controllers are directly connected to corporate networks or exposed to external network access. The potential for cascading effects means that successful exploitation could lead to broader network compromise or operational disruption across entire industrial facilities.
Mitigation strategies for CVE-2018-7759 should focus on immediate firmware updates provided by Schneider Electric, which address the buffer overflow through proper input validation and memory management. Network segmentation and access controls should be implemented to limit exposure of these devices to untrusted networks. Regular security assessments and monitoring of network traffic for anomalous patterns can help detect potential exploitation attempts. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and may map to ATT&CK techniques involving privilege escalation and execution through memory corruption. Organizations should also implement network intrusion detection systems specifically configured to identify suspicious communication patterns targeting these industrial control devices. Additionally, maintaining detailed asset inventories and implementing secure configuration management practices will help ensure that all affected devices receive timely updates and remain protected against similar vulnerabilities.