CVE-2019-5172 in PFC200
Summary
by MITRE
An exploitable command injection vulnerability exists in the iocheckd service ‘I/O-Check’ function of the WAGO PFC 200 Firmware version 03.02.02(14). An attacker can send a specially crafted packet to trigger the parsing of this cache file. At 0x1e840 the extracted ntp value from the xml file is used as an argument to /etc/config-tools/config_sntp time-server-%d=<contents of ntp node> using sprintf(). This command is later executed via a call to system(). This is done in a loop and there is no limit to how many ntp entries will be parsed from the xml file.
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Analysis
by VulDB Data Team • 04/13/2024
The vulnerability identified as CVE-2019-5172 represents a critical command injection flaw within the iocheckd service of WAGO PFC 200 industrial control systems running firmware version 03.02.02(14). This vulnerability resides in the I/O-Check functionality and stems from improper input validation during XML configuration file processing. The flaw manifests when the system parses network time protocol configuration entries from an xml cache file, creating a dangerous execution path that allows remote attackers to inject arbitrary commands into the system. The vulnerability is classified under CWE-78 as a command injection weakness, where user-supplied data is directly incorporated into system commands without adequate sanitization or validation.
The technical implementation of this vulnerability occurs at memory address 0x1e840 within the firmware's code execution flow. During the parsing process, the system extracts ntp values from xml nodes and incorporates them directly into a command string using sprintf() function. The constructed command follows the pattern /etc/config-tools/config_sntp time-server-%d=<contents of ntp node> where the ntp node contents are directly embedded without any sanitization. This command is subsequently executed through a system() call, creating a direct path for arbitrary code execution. The vulnerability is exacerbated by the lack of bounds checking or input limits during xml parsing, allowing attackers to inject multiple ntp entries that will all be processed in a loop without restriction, potentially leading to command stacking or execution of malicious payloads.
The operational impact of this vulnerability extends beyond simple command execution, presenting significant risks to industrial control systems and operational technology environments. Attackers can leverage this vulnerability to execute arbitrary commands with the privileges of the iocheckd service, potentially gaining full system control over the WAGO PFC 200 device. This could result in unauthorized access to critical industrial processes, data manipulation, or system compromise that could affect production operations. The vulnerability is particularly concerning in industrial environments where these devices often control critical infrastructure, as the attack surface could lead to cascading failures or security breaches that impact entire operational networks. The lack of input validation and command construction limitations creates an environment where attackers can effectively bypass normal security controls and execute malicious code directly on the target device.
Mitigation strategies for CVE-2019-5172 should focus on both immediate remediation and long-term security hardening. Organizations should immediately upgrade to firmware versions that address this vulnerability, as WAGO has released patches to resolve the command injection issue. Network segmentation and access controls should be implemented to limit exposure of these devices to untrusted networks, reducing the attack surface available to potential attackers. Input validation should be strengthened at the xml parsing layer to prevent injection of malicious content into system commands, and the use of parameterized commands or command whitelisting should be implemented. Security monitoring should be enhanced to detect unusual command execution patterns or unauthorized configuration changes that might indicate exploitation attempts. This vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation, making it a significant concern for industrial cybersecurity frameworks that must protect against both external attacks and insider threats targeting operational technology infrastructure.