CVE-2020-7538 in EcoStruxure Control Expert
Summary
by MITRE • 11/20/2020
A CWE-754: Improper Check for Unusual or Exceptional Conditions vulnerability exists in PLC Simulator on EcoStruxureª Control Expert (now Unity Pro) (all versions) that could cause a crash of the PLC simulator present in EcoStruxureª Control Expert software when receiving a specially crafted request over Modbus.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 12/09/2020
The vulnerability identified as CVE-2020-7538 represents a critical weakness in the PLC Simulator component of EcoStruxureª Control Expert software, which has been rebranded as Unity Pro. This issue manifests as a CWE-754 improper check for unusual or exceptional conditions, a classification that falls under the broader category of improper error handling within industrial control systems. The vulnerability specifically affects all versions of the software, indicating a widespread exposure across the product lineage. The flaw resides in how the PLC simulator processes incoming Modbus requests, creating a scenario where legitimate network traffic can trigger unexpected system behavior.
The technical implementation of this vulnerability exploits the absence of proper validation mechanisms within the Modbus protocol handler of the PLC simulator. When the software receives a specially crafted Modbus request, the lack of robust input validation causes the application to enter an undefined state that ultimately results in a crash. This behavior stems from insufficient error checking routines that fail to properly identify and handle malformed or unexpected data patterns. The vulnerability demonstrates a classic example of how industrial control system software can fail to properly sanitize input data, particularly when dealing with protocols that are commonly used in industrial environments such as Modbus.
From an operational standpoint, this vulnerability presents significant risks to industrial environments that rely on EcoStruxureª Control Expert for simulation and development purposes. The crash condition can lead to complete system unavailability during critical development phases, potentially causing project delays and operational disruptions. In production environments where this software might be used for testing or training purposes, the vulnerability could provide an attack vector for adversaries seeking to disrupt operations or establish a foothold for more sophisticated attacks. The impact extends beyond simple service disruption as it can compromise the integrity of development processes and potentially expose underlying system configurations.
The exploitation of this vulnerability aligns with ATT&CK technique T1499.004, which involves network disruption through service exhaustion or denial of service attacks. Security practitioners should recognize that this vulnerability represents a potential entry point for attackers seeking to compromise industrial control system environments. The lack of proper input validation creates an opportunity for attackers to craft specific Modbus packets that can trigger the crash condition, potentially leading to more severe consequences if the system is part of a larger industrial network architecture. Organizations using this software should implement network segmentation and monitoring to detect unusual Modbus traffic patterns that might indicate exploitation attempts.
Mitigation strategies for CVE-2020-7538 should focus on implementing proper input validation and error handling mechanisms within the PLC simulator. System administrators should ensure that all instances of EcoStruxureª Control Expert are updated to the latest available versions that contain patches addressing this vulnerability. Network-level protections including Modbus traffic filtering and monitoring solutions can help detect and prevent exploitation attempts. Additionally, implementing proper access controls and limiting network exposure of the PLC simulator can reduce the attack surface. Organizations should also consider implementing network segmentation to isolate development environments from critical operational systems, following the principle of least privilege and reducing potential impact if exploitation occurs. The vulnerability serves as a reminder of the importance of robust error handling in industrial control systems and the need for comprehensive security testing of all components within industrial automation environments.