CVE-2017-6034 in Cove
Summary
by MITRE
An Authentication Bypass by Capture-Replay issue was discovered in Schneider Electric Modicon Modbus Protocol. Sensitive information is transmitted in cleartext in the Modicon Modbus protocol, which may allow an attacker to replay the following commands: run, stop, upload, and download.
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Analysis
by VulDB Data Team • 05/29/2026
The vulnerability identified as CVE-2017-6034 represents a critical authentication bypass flaw within Schneider Electric Modicon Modbus protocol implementations that fundamentally undermines the security posture of industrial control systems. This issue stems from the protocol's inherent design weakness where sensitive operational commands are transmitted without proper authentication mechanisms, creating a capture-replay attack vector that can be exploited by malicious actors. The Modicon Modbus protocol, widely deployed in industrial environments for communication between programmable logic controllers and other devices, fails to implement adequate cryptographic protections for its data transmission channels, leaving critical system operations exposed to unauthorized access and manipulation.
The technical flaw manifests through the protocol's transmission of commands such as run, stop, upload, and download in cleartext format without any form of authentication verification or encryption. This design oversight creates a scenario where an attacker positioned within the network can capture legitimate communication traffic containing these operational commands and subsequently replay them at will to execute unauthorized actions against the target system. The vulnerability specifically affects the Modicon series of industrial devices that utilize the Modbus protocol for communication, making it particularly dangerous in environments where operational technology systems require robust security controls to prevent unauthorized access to critical infrastructure components.
The operational impact of this vulnerability extends far beyond simple data exposure, as it enables attackers to gain full control over industrial processes through the execution of critical commands that can halt operations, modify system configurations, or extract sensitive operational data. When an attacker successfully exploits this vulnerability, they can perform unauthorized system control operations that may result in production disruptions, safety hazards, or even physical damage to industrial equipment. The cleartext transmission of commands means that any network monitoring tools or security devices that capture this traffic can immediately identify and potentially exploit the vulnerability, making the attack surface significantly larger than initially apparent. This authentication bypass capability directly violates fundamental security principles and creates a persistent threat vector that remains active as long as the vulnerable protocol implementation exists.
Organizations affected by this vulnerability should implement immediate mitigations including network segmentation to isolate industrial control systems from general enterprise networks, deployment of network monitoring solutions specifically designed to detect and alert on Modbus protocol anomalies, and implementation of secure remote access solutions that provide proper authentication and encryption for system administration. The vulnerability aligns with CWE-312 (Cleartext Storage of Sensitive Information) and CWE-310 (Cryptography Issues) classifications, and represents a significant concern from the ATT&CK framework under the T1071.001 (Application Layer Protocol: Web Protocols) and T1566 (Phishing) tactics as attackers can leverage this weakness to gain unauthorized access to industrial control systems. Additionally, the vulnerability demonstrates characteristics consistent with ATT&CK technique T1059 (Command and Scripting Interpreter) and T1021.001 (Remote Services: Remote Desktop Protocol) when attackers use the compromised system to execute further malicious activities within the industrial environment. Long-term remediation requires upgrading to secure protocol implementations that incorporate proper authentication mechanisms, encryption, and integrity checking to prevent the replay attack scenarios that make this vulnerability so dangerous in industrial control system environments.