CVE-2019-5169 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). 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 0x1e900 the extracted gateway value from the xml file is used as an argument to /etc/config-tools/config_default_gateway number=0 state=enabled value=<contents of gateway 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-2019-5169 represents a critical command injection flaw within the WAGO PFC 200 industrial control device firmware version 03.02.02(14). This issue resides in the iocheckd service's I/O-Check function, which processes XML cache files stored in specific device locations. The vulnerability stems from insufficient input validation and sanitization when parsing gateway configuration data from XML files, creating a pathway for arbitrary command execution. The flaw manifests at memory address 0x1e900 where the extracted gateway value from the XML file is directly incorporated into a system command using sprintf() function without proper sanitization. This design flaw aligns with CWE-78, which specifically addresses improper neutralization of special elements used in OS commands, making it susceptible to command injection attacks. The attack vector requires an attacker to place a malicious XML cache file in a predetermined location on the device, followed by sending a specially crafted packet that triggers the parsing of this cache file, effectively bypassing normal authentication mechanisms.
The operational impact of this vulnerability extends beyond typical network security concerns due to the industrial nature of WAGO PFC 200 devices, which are commonly deployed in critical infrastructure environments such as manufacturing plants, oil and gas facilities, and power generation systems. When exploited, this command injection vulnerability allows attackers to execute arbitrary operating system commands with the privileges of the iocheckd service, potentially leading to complete system compromise. The vulnerability's exploitation chain demonstrates a classic command injection pattern where user-controllable input flows directly into system execution contexts, as defined by the ATT&CK framework's T1059.001 technique for command and scripting interpreter. The specific implementation uses a sprintf() function call to format a command string that includes the unsanitized gateway value, which is then passed to the system() function for execution, creating a direct path for malicious command injection. This vulnerability represents a significant risk in industrial control systems where device availability and integrity are paramount, as attackers could potentially disrupt operations, modify critical configurations, or escalate privileges to gain full administrative control over the affected device.
Mitigation strategies for CVE-2019-5169 must address both immediate protection and long-term system hardening measures. Organizations should implement network segmentation and access controls to limit exposure of affected WAGO PFC 200 devices to untrusted networks, as recommended by NIST SP 800-53 controls for industrial control systems. The most effective immediate solution involves applying the vendor-provided firmware update that addresses the XML parsing vulnerability and implements proper input sanitization for gateway values. Network administrators should also consider implementing file integrity monitoring solutions to detect unauthorized modifications to XML cache files and system configuration directories. Additional protective measures include disabling unnecessary network services, implementing strict file access controls on the device filesystem, and monitoring for suspicious command execution patterns through security information and event management systems. The vulnerability's classification as a command injection flaw necessitates implementing input validation at multiple layers, including XML schema validation and parameter sanitization, to prevent similar issues in other components of the industrial control system. Security teams should also conduct regular vulnerability assessments and penetration testing specifically targeting industrial control systems to identify and remediate similar weaknesses in operational technology environments.