CVE-2020-7562 in Modicon M340
Summary
by MITRE • 11/18/2020
A CWE-125: Out-of-Bounds Read 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 a segmentation fault or a buffer overflow 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 identified as CVE-2020-7562 represents a critical out-of-bounds read flaw classified under CWE-125 within the web server component of several legacy Modicon PLC platforms including M340, Quantum, and Premium series. This weakness manifests specifically when the affected controllers process file uploads via FTP protocols, creating a scenario where maliciously crafted files can trigger memory access violations. The vulnerability affects not only the primary controllers but also their associated communication modules, amplifying the potential impact across industrial control systems. The affected systems operate within critical infrastructure environments where reliability and security are paramount, making this vulnerability particularly concerning for operational technology networks.
The technical implementation of this vulnerability stems from insufficient input validation mechanisms within the web server's file handling routines. When a specially crafted file is uploaded through the FTP interface, the system fails to properly bounds-check the data before processing it, leading to memory access beyond allocated buffer boundaries. This improper memory handling can result in segmentation faults that cause system crashes or more severe buffer overflow conditions that may allow attackers to execute arbitrary code. The flaw exists at the application layer where the web server component processes file uploads without adequate sanitization of user-supplied data, creating an attack surface that can be exploited by remote threat actors.
The operational impact of this vulnerability extends beyond simple system instability to potentially compromise entire industrial control networks. When segmentation faults occur due to out-of-bounds reads, the affected controllers may experience unexpected restarts or complete system failures, leading to operational disruptions in critical manufacturing or infrastructure processes. The buffer overflow conditions present in some exploitation scenarios could enable attackers to gain unauthorized access to system resources, potentially allowing for privilege escalation and persistent access to industrial control systems. These vulnerabilities are particularly dangerous in environments where continuous operation is required, as any disruption can result in significant financial losses and safety risks.
Mitigation strategies for CVE-2020-7562 should focus on immediate network segmentation and access controls to limit exposure of affected devices to untrusted networks. Organizations must implement strict FTP access controls and consider disabling unnecessary web server functionality on affected controllers. The implementation of network monitoring solutions can help detect anomalous file upload patterns that may indicate exploitation attempts. Additionally, regular firmware updates from the vendor should be applied as patches become available, though legacy systems may require careful assessment due to potential compatibility issues. Security teams should also consider implementing intrusion detection systems specifically configured to monitor for FTP protocol anomalies and file transfer behaviors that could indicate exploitation attempts, aligning with ATT&CK framework techniques related to command and control communications and credential access.