CVE-2018-7809 in M340
Summary
by MITRE
An Unverified Password Change vulnerability exists in the embedded web servers in all Modicon M340, Premium, Quantum PLCs and BMXNOR0200 which could allow an unauthenticated remote user to access the password delete function of the web server.
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Analysis
by VulDB Data Team • 04/16/2020
The vulnerability identified as CVE-2018-7809 represents a critical security flaw in industrial control systems manufactured by Schneider Electric, specifically affecting Modicon M340, Premium, Quantum PLCs, and BMXNOR0200 devices. This weakness resides within the embedded web servers of these industrial programmable logic controllers, creating a significant entry point for unauthorized remote access. The vulnerability stems from insufficient authentication mechanisms that fail to properly verify user credentials before allowing access to critical administrative functions, particularly the password deletion functionality. This flaw allows an attacker to exploit the web server interface without requiring valid authentication credentials, effectively bypassing the normal security controls that should protect industrial control systems from unauthorized access.
The technical implementation of this vulnerability demonstrates a classic lack of input validation and authentication verification within the web server component of these industrial devices. When an unauthenticated remote user accesses the web server interface, the system fails to properly validate the user's identity before granting access to administrative functions. The password delete function operates without proper authentication checks, meaning that any remote attacker who can reach the device's web interface can potentially execute this function. This represents a fundamental flaw in the principle of least privilege and proper access control implementation. According to CWE classification, this vulnerability maps to CWE-287 which describes improper authentication issues in software systems. The flaw essentially creates a backdoor mechanism that allows attackers to manipulate user credentials without proper authorization, potentially leading to complete system compromise.
The operational impact of CVE-2018-7809 extends beyond simple unauthorized access, as it directly threatens the integrity and availability of industrial control systems. In industrial environments, these PLCs control critical infrastructure operations, manufacturing processes, and safety systems where unauthorized access could lead to production disruptions, safety hazards, or even physical damage to equipment. The remote nature of the vulnerability means that attackers can exploit this weakness from anywhere on the network, eliminating the need for physical access or local network presence. This characteristic significantly increases the attack surface and the potential for large-scale disruptions. The vulnerability aligns with ATT&CK technique T1078 which covers valid accounts usage and can be leveraged for lateral movement within industrial networks, potentially enabling attackers to escalate privileges and access additional systems.
Mitigation strategies for this vulnerability require immediate attention from system administrators and industrial security teams responsible for these devices. The primary recommendation involves applying firmware updates provided by Schneider Electric to address the authentication bypass flaw in the embedded web servers. Organizations should also implement network segmentation to isolate these industrial control systems from general network access, reducing the attack surface for remote exploitation. Network access controls should be configured to restrict access to the web server ports only to authorized personnel and systems. Additionally, implementing network monitoring and intrusion detection systems can help identify suspicious access attempts to these devices. Regular security assessments and vulnerability scanning should be conducted to identify similar authentication weaknesses in other industrial control systems within the organization. The remediation process should also include disabling unnecessary web server functionality when not required for operational purposes, following the principle of least functionality. Organizations should also establish proper change management procedures to ensure that all updates and configuration changes are properly tested and deployed to maintain system integrity while addressing this specific vulnerability.