CVE-2020-7564 in Modicon M340
Summary
by MITRE • 11/18/2020
A CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') vulnerability exists in the Web Server on Modicon M340, Modicon Quantum and Modicon Premium Legacy offers and their Communication Modules (see notification for details) which could cause write access and the execution of commands when uploading a specially crafted file on the controller over FTP.
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Analysis
by VulDB Data Team • 05/30/2026
The vulnerability described in CVE-2020-7564 represents a classic buffer overflow condition that affects legacy industrial control systems manufactured by Schneider Electric. This flaw specifically impacts the web server component embedded within Modicon M340, Modicon Quantum, and Modicon Premium legacy offerings along with their associated communication modules. The vulnerability stems from inadequate input validation during file upload operations, particularly when processing files transmitted via FTP protocol to the controller. The root cause aligns with CWE-120, which categorizes buffer overflows occurring when programs copy data into buffers without properly checking the source data size against the destination buffer capacity. This fundamental flaw creates a pathway for attackers to manipulate memory layout and potentially execute arbitrary code within the controller environment.
The operational impact of this vulnerability extends beyond simple data corruption, as it provides adversaries with the capability to achieve write access and command execution on affected industrial controllers. When an attacker uploads a maliciously crafted file through the FTP interface, the insufficient buffer size checking allows the overflow to occur, potentially overwriting adjacent memory locations including return addresses, function pointers, or other critical control data structures. This condition creates an opportunity for privilege escalation and persistent access to the industrial control environment, which could result in unauthorized modifications to control logic, disruption of industrial processes, or even physical safety hazards in critical infrastructure environments. The attack vector specifically targets the communication modules, suggesting that the vulnerability may be exploitable through network-based attacks without requiring physical access to the devices.
The security implications of this vulnerability align with several ATT&CK framework techniques including T1059 Command and Scripting Interpreter and T1078 Valid Accounts, as successful exploitation would likely enable attackers to establish persistent command execution capabilities on industrial control systems. The affected legacy systems represent high-value targets within industrial control environments where operational technology security is often less mature than traditional enterprise IT security measures. Organizations utilizing these Modicon legacy platforms face significant risk due to the combination of the buffer overflow vulnerability and the potential for remote code execution, particularly in environments where these controllers operate in closed-loop industrial processes. The vulnerability's exploitation requires network connectivity to the FTP service and proper authentication credentials, but once achieved, provides attackers with substantial control over the affected industrial processes.
Mitigation strategies for CVE-2020-7564 should prioritize immediate implementation of network segmentation and access controls to restrict FTP access to authorized personnel only. Organizations must ensure that all affected legacy systems are properly patched through official Schneider Electric updates, as these devices may no longer receive support from the vendor. Network monitoring should be enhanced to detect suspicious FTP traffic patterns and file upload activities that could indicate exploitation attempts. Additionally, implementing strict input validation controls on the web server component and disabling unnecessary FTP services where possible will reduce the attack surface. Regular security assessments of industrial control environments should include vulnerability scanning specifically targeting legacy industrial protocols and components, as these systems often present unique security challenges that require specialized mitigation approaches. The vulnerability underscores the critical need for industrial organizations to maintain comprehensive asset inventories and implement robust security measures for legacy industrial control systems that may not receive regular security updates from vendors.