CVE-2020-7563 in Modicon M340
Summary
by MITRE • 11/18/2020
A CWE-787: Out-of-bounds Write 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 corruption of data, a crash, or code execution when uploading a specially crafted file on the controller over FTP.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 05/30/2026
The vulnerability identified as CVE-2020-7563 represents a critical out-of-bounds write flaw classified under CWE-787 within the web server component of several Modicon series controllers including the M340, Quantum, and Premium Legacy offerings along with their associated communication modules. This issue manifests during file upload operations conducted via FTP protocol, creating a significant security risk for industrial control systems deployed in critical infrastructure environments.
The technical implementation of this vulnerability stems from insufficient bounds checking within the web server's file processing logic when handling uploaded content. When a maliciously crafted file is transmitted through FTP to the controller, the system fails to validate the boundaries of memory allocations, leading to unauthorized memory writes beyond allocated buffers. This memory corruption can occur during parsing or validation of the uploaded file's content, particularly when the web server attempts to process file metadata or extract specific data segments for further handling.
The operational impact of this vulnerability extends beyond simple system instability, presenting potential pathways for unauthorized code execution and complete system compromise. An attacker who successfully exploits this flaw could cause data corruption that affects controller operations, leading to system crashes or complete service denial. In industrial control environments, such disruptions could result in production halts, safety system failures, or even physical damage to equipment, making this vulnerability particularly dangerous for critical infrastructure sectors.
The attack surface for this vulnerability is primarily limited to environments where FTP access is enabled on Modicon controllers and where attackers can upload files through the web server interface. This scenario typically occurs in network configurations where legacy industrial systems have not been properly secured or where administrative access has been compromised. The vulnerability is particularly concerning because it affects multiple generations of Modicon controllers, indicating a widespread exposure across industrial automation platforms.
Mitigation strategies should focus on immediate network segmentation to restrict FTP access to authorized personnel only, implementation of strict file validation procedures, and regular firmware updates from Schneider Electric to address the specific memory handling flaws. Organizations should also consider disabling unnecessary web server functionality and implementing intrusion detection systems to monitor for suspicious FTP upload activities. The vulnerability aligns with ATT&CK technique T1195.001 for 'Supply Chain Compromise' and T1071.004 for 'Application Layer Protocol: DNS' when considering potential lateral movement after initial compromise. Compliance with NIST SP 800-82 guidelines for industrial control systems security and IEC 62443 standards should be maintained to ensure proper operational security practices are implemented across affected industrial networks.