CVE-2019-5174 in PFC200
Summary
by MITRE
An exploitable command injection vulnerability exists in the iocheckd service ‘I/O-Check’ function of the WAGO PFC 200 version 03.02.02(14). A specially crafted XML cache file written to a specific location on the device can be used to inject OS commands. An attacker can send a specially crafted packet to trigger the parsing of this cache file.At 0x1e9fc the extracted subnetmask value from the xml file is used as an argument to /etc/config-tools/config_interfaces interface=X1 state=enabled subnet-mask=<contents of subnetmask node> using sprintf(). This command is later executed via a call to system().
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Analysis
by VulDB Data Team • 04/13/2024
The vulnerability identified as CVE-2019-5174 represents a critical command injection flaw within the iocheckd service of WAGO PFC 200 devices running firmware version 03.02.02(14). This issue falls under the CWE-78 category of OS Command Injection, where untrusted data is directly incorporated into operating system commands without proper sanitization or validation. The vulnerability specifically manifests in the I/O-Check function that processes XML cache files, creating a pathway for remote attackers to execute arbitrary commands on the affected device. The flaw resides in the improper handling of user-supplied data during XML parsing operations, where the subnetmask value extracted from the XML configuration file is directly passed to a system command through sprintf() function without adequate input validation or sanitization.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious XML cache file containing specially formatted subnetmask data that includes shell metacharacters. When the iocheckd service processes this cache file at memory address 0x1e9fc, it extracts the subnetmask value and incorporates it into a command string that is subsequently executed via the system() function call. This creates a classic command injection scenario where attacker-controlled data becomes part of the command line arguments passed to the operating system shell. The vulnerable code structure demonstrates poor input validation practices that are commonly associated with insecure coding patterns and violate fundamental security principles of input sanitization and command construction.
The operational impact of this vulnerability is severe and multifaceted, as it provides attackers with complete control over the affected WAGO PFC 200 device. Successful exploitation enables remote code execution with the privileges of the iocheckd service, which typically runs with elevated permissions on industrial control systems. This could lead to unauthorized access to critical industrial processes, data manipulation, or even complete system compromise. The vulnerability is particularly concerning in industrial environments where these devices are deployed, as it could potentially disrupt critical infrastructure operations and create persistent backdoors for attackers. The attack vector requires only the ability to send specially crafted packets to the device, making it accessible to remote adversaries without physical access requirements.
Security mitigations for CVE-2019-5174 should focus on immediate firmware updates from WAGO to address the root cause of the vulnerability. Network segmentation and access controls should be implemented to limit exposure of these devices to untrusted networks, while monitoring systems should be deployed to detect suspicious XML file modifications or command execution patterns. Input validation mechanisms should be strengthened to prevent untrusted data from being incorporated into system commands, and the principle of least privilege should be enforced to limit the capabilities of the iocheckd service. Additionally, organizations should implement regular security assessments of industrial control systems to identify similar vulnerabilities and maintain up-to-date threat intelligence to detect exploitation attempts. The vulnerability demonstrates the importance of secure coding practices and proper input validation in industrial control systems, where security failures can have significant operational and safety implications.