CVE-2019-6529 in PR100088 Modbus Gateway
Summary
by MITRE
An attacker could specially craft an FTP request that could crash the PR100088 Modbus gateway versions prior to release R02 (or Software Version 1.1.13166).
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Analysis
by VulDB Data Team • 05/09/2020
The CVE-2019-6529 vulnerability represents a critical denial of service condition affecting the PR100088 Modbus gateway device, specifically impacting versions prior to release R02 or software version 1.1.13166. This vulnerability resides within the network communication handling mechanisms of industrial control systems, where the device fails to properly validate incoming FTP requests. The flaw demonstrates a classic buffer overflow or input validation issue that allows malicious actors to craft specially formatted requests designed to trigger system instability. The Modbus protocol, widely used in industrial automation and SCADA systems, operates within critical infrastructure environments where reliability and uptime are paramount. When exploited, this vulnerability can cause the gateway to crash and restart, potentially disrupting industrial processes and creating operational gaps that could have cascading effects on production systems.
The technical implementation of this vulnerability involves the manipulation of FTP protocol handling within the Modbus gateway firmware, where insufficient input validation leads to system crash conditions. The device's inability to properly parse or reject malformed FTP requests creates a pathway for attackers to cause unexpected behavior through carefully constructed network traffic. This vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a failure in proper input validation and error handling within embedded industrial systems. The attack vector typically involves sending crafted FTP commands that exceed expected parameter limits or contain malformed data structures, causing the gateway's memory management to fail and resulting in system termination or reboot cycles.
The operational impact of CVE-2019-6529 extends beyond simple service disruption, particularly within industrial environments where continuous operation is essential. When the PR100088 Modbus gateway crashes, it can interrupt communication between field devices and control systems, potentially causing production line stoppages, data loss, or safety system failures. The vulnerability affects devices deployed in manufacturing facilities, power generation plants, and other critical infrastructure sectors where Modbus gateways serve as crucial communication bridges. The restart behavior creates additional operational challenges as the system must reestablish connections and potentially lose configuration data, while the periodic nature of such crashes can make them difficult to detect and remediate. Organizations using affected systems face potential regulatory compliance issues, as industrial control systems must maintain availability and reliability standards.
Mitigation strategies for CVE-2019-6529 primarily focus on firmware updates and network segmentation measures. The most effective solution involves upgrading the PR100088 Modbus gateway to release R02 or later software versions that contain proper input validation and error handling mechanisms. Network administrators should implement firewall rules to restrict FTP access to only trusted sources and consider disabling unnecessary FTP services when possible. The vulnerability demonstrates the importance of maintaining current firmware versions in industrial environments, as older releases often lack security patches and proper input validation. Security teams should also implement monitoring solutions to detect unusual gateway restart patterns or network traffic anomalies that might indicate exploitation attempts. Organizations should follow ATT&CK framework tactics related to defense in depth, including network segmentation, access control, and regular security assessments to identify and remediate similar vulnerabilities across their industrial control system infrastructure.