CVE-2018-7760 in Modicon M340
Summary
by MITRE
An authorization bypass vulnerability exists in Schneider Electric's Modicon M340, Modicon Premium, Modicon Quantum PLC, BMXNOR0200. Requests to CGI functions allow malicious users to bypass authorization.
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Analysis
by VulDB Data Team • 01/27/2020
The vulnerability identified as CVE-2018-7760 represents a critical authorization bypass flaw affecting Schneider Electric's Modicon M340, Modicon Premium, Modicon Quantum PLC, and BMXNOR0200 devices. This weakness resides within the web-based configuration interface implementation, specifically in how the system handles requests to Common Gateway Interface functions. The flaw allows unauthenticated or improperly authenticated users to gain access to administrative functions that should be restricted to authorized personnel only, fundamentally undermining the security model of these industrial control systems.
The technical implementation of this vulnerability stems from insufficient input validation and authentication checks within the CGI handler components of the affected PLC firmware. When users submit requests to specific CGI endpoints, the system fails to properly verify user credentials or authorization levels before executing privileged operations. This design flaw creates a pathway for malicious actors to exploit the system's web interface and perform administrative actions without proper authentication. The vulnerability is particularly concerning because it affects the core configuration and control functions of industrial automation systems, potentially allowing attackers to modify critical operational parameters or access sensitive system information.
The operational impact of this authorization bypass vulnerability extends beyond simple unauthorized access to encompass potential disruption of industrial processes and compromise of operational technology environments. Attackers could manipulate programmable logic controller configurations, alter safety parameters, or access confidential operational data that should remain protected. This vulnerability directly affects the integrity and availability of industrial control systems, potentially leading to production disruptions, safety hazards, or even physical damage to equipment. The implications are particularly severe in environments where these PLCs control critical infrastructure or manufacturing processes, as the unauthorized access could result in significant financial losses or operational failures.
Organizations operating affected Schneider Electric PLC devices should implement immediate mitigations including firmware updates from Schneider Electric, network segmentation to isolate these devices from general network access, and strict access controls for web-based interfaces. The vulnerability aligns with CWE-285, which addresses improper authorization in software systems, and maps to ATT&CK technique T1078 for valid accounts and T1566 for spearphishing, as attackers could potentially leverage this flaw to establish persistent access or escalate privileges within industrial environments. Security monitoring should focus on unusual web interface access patterns and unauthorized configuration changes, while network administrators should consider implementing web application firewalls to protect against exploitation attempts targeting these specific CGI endpoints.