CVE-2018-7811 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 change password function of the web server
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Analysis
by VulDB Data Team • 04/16/2020
The vulnerability identified as CVE-2018-7811 represents a critical security flaw in industrial control systems manufactured by Schneider Electric, specifically affecting Modicon M340, Premium, Quantum PLCs and BMXNOR0200 devices. This issue stems from insufficient authentication mechanisms within the embedded web servers of these industrial devices, creating a pathway for unauthorized remote access. The flaw allows an attacker to exploit the password change function without requiring any valid credentials, effectively bypassing the standard authentication process that should normally be required to modify user access privileges. This vulnerability is particularly concerning within industrial environments where operational technology systems require robust security measures to prevent unauthorized access to critical infrastructure.
The technical implementation of this vulnerability resides in the web server component of these industrial devices, which fails to properly validate user credentials before permitting access to administrative functions including password modification. According to CWE classification, this vulnerability maps to CWE-287 which describes improper authentication scenarios where systems do not adequately verify user identities before granting access to protected functions. The flaw manifests as an insufficient verification mechanism that allows any remote attacker to directly invoke the password change functionality through the web interface. This typically occurs when the web server does not properly check for authentication tokens or session validity before processing password change requests, enabling attackers to manipulate the web server's password change endpoint without prior authorization. The vulnerability specifically affects the embedded web server implementations within these PLCs, which are designed to provide remote management capabilities but lack proper access control enforcement.
The operational impact of CVE-2018-7811 extends beyond simple unauthorized access to potentially catastrophic consequences for industrial operations. An attacker who successfully exploits this vulnerability could gain persistent access to the industrial control system, potentially leading to unauthorized modifications of critical control parameters, disruption of production processes, or even complete system compromise. The remote nature of this vulnerability means that attackers do not require physical access to the devices, significantly expanding the attack surface and making the systems more vulnerable to exploitation. This flaw particularly affects environments where these PLCs are connected to networks or the internet, as it enables attackers to perform password changes that could lock out legitimate administrators or grant themselves persistent access to the system. The vulnerability could also facilitate lateral movement within industrial networks, as compromised PLCs often serve as entry points for broader network infiltration.
Mitigation strategies for CVE-2018-7811 should focus on both immediate protective measures and long-term security enhancements. Immediate actions include isolating affected devices from untrusted networks, implementing network segmentation to limit access to these industrial control systems, and applying firmware updates provided by Schneider Electric to address the authentication flaw. Organizations should also consider disabling unnecessary web server functionality when it is not required for operations, as this reduces the attack surface available to potential attackers. The implementation of network access controls using firewalls and intrusion detection systems can help monitor and restrict access attempts to these vulnerable web interfaces. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving credential access and defense evasion, as attackers could use the compromised credentials to maintain persistence or move laterally within the industrial network. Additionally, organizations should conduct comprehensive vulnerability assessments to identify all similar devices within their industrial control systems that may be affected by similar authentication flaws, and establish robust monitoring procedures to detect unauthorized access attempts to these critical systems.