CVE-2017-6026 in Modicon M241
Summary
by MITRE
A Use of Insufficiently Random Values issue was discovered in Schneider Electric Modicon PLCs Modicon M241, firmware versions prior to Version 4.0.5.11, and Modicon M251, firmware versions prior to Version 4.0.5.11. The session numbers generated by the web application are lacking randomization and are shared between several users. This may allow a current session to be compromised.
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Analysis
by VulDB Data Team • 09/19/2024
The vulnerability identified as CVE-2017-6026 represents a critical weakness in Schneider Electric Modicon PLCs that affects both the M241 and M251 series devices operating with firmware versions prior to 4.0.5.11. This issue stems from the improper implementation of random number generation within the web application interface of these industrial control systems, creating a significant security risk that directly impacts the integrity of session management processes. The flaw manifests in the insufficient entropy provided by the session number generation algorithm, which fails to produce truly random values necessary for secure authentication and session tracking.
The technical implementation of this vulnerability demonstrates a clear violation of fundamental cryptographic principles and security best practices. When session numbers are generated using insufficiently random values, they become predictable and susceptible to exploitation by malicious actors who can potentially guess or derive valid session identifiers. The sharing of session numbers between multiple users further compounds the risk, as it creates a scenario where compromising one session could potentially provide access to multiple user accounts or system functionalities. This weakness directly maps to CWE-330, which specifically addresses the use of insufficiently random values in security contexts, and represents a failure in the proper implementation of cryptographically secure random number generation mechanisms that are essential for maintaining system integrity and preventing unauthorized access.
From an operational standpoint, this vulnerability poses severe implications for industrial control systems where these PLCs are deployed. The compromised session management creates opportunities for session hijacking attacks, where an attacker could potentially take over active sessions and gain unauthorized access to critical control functions. This risk is particularly concerning in industrial environments where these devices control physical processes and safety systems, as unauthorized access could lead to operational disruptions, safety hazards, or even physical damage to equipment and facilities. The vulnerability essentially undermines the authentication mechanisms that are supposed to protect industrial control systems from unauthorized access, creating a pathway for attackers to manipulate control parameters or gain persistent access to the system.
The exploitation of this vulnerability aligns with techniques described in the MITRE ATT&CK framework under the Tactic of Credential Access and Persistence, specifically targeting session management weaknesses that allow for unauthorized access to systems. Organizations utilizing these affected PLCs face significant operational risks, particularly in critical infrastructure sectors such as manufacturing, energy, and water treatment facilities where the integrity of control systems is paramount. The lack of proper randomization in session generation creates a predictable attack surface that can be systematically exploited through brute force or pattern analysis techniques, making it particularly dangerous in environments where physical security measures may be insufficient to prevent network-based attacks.
Mitigation strategies for this vulnerability require immediate firmware updates to versions 4.0.5.11 or later, which address the random number generation implementation and correct the session management flaws. Organizations should also implement network segmentation to limit access to these devices, deploy intrusion detection systems to monitor for suspicious session activity, and establish regular security assessments of industrial control systems. Additionally, implementing strong access controls, disabling unnecessary web interfaces, and maintaining detailed audit logs of system access can help detect and prevent exploitation attempts. The remediation process should include comprehensive testing to ensure that the updated firmware properly addresses the randomization issues and that no other session management vulnerabilities exist within the industrial control environment.