CVE-2017-6028 in Modicon M241
Summary
by MITRE
An Insufficiently Protected Credentials issue was discovered in Schneider Electric Modicon PLCs Modicon M241, all firmware versions, and Modicon M251, all firmware versions. Log-in credentials are sent over the network with Base64 encoding leaving them susceptible to sniffing. Sniffed credentials could then be used to log into the web application.
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Analysis
by VulDB Data Team • 12/30/2020
The vulnerability identified as CVE-2017-6028 represents a critical weakness in Schneider Electric's Modicon series programmable logic controllers that affects both the M241 and M251 models across all firmware versions. This security flaw resides in the authentication mechanism of these industrial control devices, specifically in how they handle credential transmission over network communications. The issue manifests as an insufficiently protected credentials vulnerability that fundamentally undermines the security posture of these industrial systems.
The technical implementation of this vulnerability stems from the use of Base64 encoding for transmitting login credentials over network connections rather than implementing proper cryptographic protection mechanisms. Base64 encoding is a simple binary-to-text encoding scheme that is easily reversible and does not provide any form of encryption or authentication. When credentials are transmitted using this method, they remain in a readable format that can be easily intercepted and decoded by any network monitoring tool or malicious actor with access to the network traffic. This weakness directly violates security best practices and industry standards such as those outlined in CWE-312, which specifically addresses the exposure of sensitive information through improper encoding.
The operational impact of this vulnerability extends far beyond simple credential theft, as it provides attackers with unauthorized access to industrial control systems that manage critical manufacturing processes. Once sniffed credentials are obtained, malicious actors can establish legitimate web sessions with the affected PLCs, potentially gaining full administrative control over the industrial processes. This access could enable attackers to modify control parameters, disrupt production workflows, or even cause physical damage to equipment. The vulnerability affects industrial environments where these devices operate, including manufacturing plants, process control facilities, and other critical infrastructure sectors where the compromise of control systems can have severe operational and safety implications.
The security implications of CVE-2017-6028 align with several ATT&CK framework techniques including credential access through network sniffing and privilege escalation via valid accounts. This vulnerability represents a classic case of weak cryptography implementation in industrial control systems, where the assumption that network traffic is secure leads to dangerous exposure of authentication credentials. Organizations utilizing Schneider Electric Modicon PLCs must recognize that this vulnerability creates a persistent risk that cannot be mitigated through traditional network segmentation alone, as the credentials are exposed at the application layer during authentication. The lack of proper encryption or authentication protocols in the communication stack of these devices makes them particularly vulnerable to man-in-the-middle attacks and passive network monitoring.
Mitigation strategies for this vulnerability require immediate implementation of network security controls including the deployment of network segmentation, encryption of industrial communications, and regular monitoring for suspicious authentication attempts. Organizations should implement proper network access controls to limit exposure of these devices to untrusted networks and consider deploying secure remote access solutions that utilize strong authentication mechanisms. The vulnerability also highlights the importance of secure coding practices in industrial software development and the need for regular security assessments of control system components. Given that this affects all firmware versions, the most effective immediate solution involves network-level protections rather than firmware updates, as the underlying issue is in the communication protocol implementation rather than specific firmware flaws.