CVE-2019-5178 in PFC200
Summary
by MITRE
An exploitable stack buffer overflow vulnerability vulnerability exists in the iocheckd service ‘I/O-Check’ functionality of 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. The destination buffer sp+0x440 is overflowed with the call to sprintf() for any hostname values that are greater than 1024-len(‘/etc/config-tools/change_hostname hostname=‘) in length. A hostname value of length 0x3fd will cause the service to crash.
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Analysis
by VulDB Data Team • 04/13/2024
The vulnerability described in CVE-2019-5178 represents a critical stack buffer overflow flaw within the iocheckd service of WAGO PFC 200 industrial control devices running firmware version 03.02.02(14). This issue resides in the I/O-Check functionality, which is a core component responsible for monitoring and managing input/output operations in industrial automation environments. The flaw manifests when the system processes specially crafted network packets designed to exploit the hostname parsing mechanism, creating a dangerous condition that can lead to arbitrary code execution or system compromise. The vulnerability specifically affects the handling of hostname values through the configuration interface, where the system fails to properly validate input length before processing.
The technical implementation of this vulnerability stems from improper bounds checking within the sprintf() function call, which occurs when processing hostname values submitted through the /etc/config-tools/change_hostname command interface. The destination buffer located at sp+0x440 has a fixed size limitation that cannot accommodate hostname values exceeding 1024 minus the length of the command prefix. This creates a predictable overflow condition where input data exceeding the buffer capacity causes memory corruption. The precise threshold of 0x3fd (1021 decimal) bytes demonstrates a mathematical boundary condition where the system's buffer management fails to account for the complete input processing chain. This particular buffer overflow scenario aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a classic example of insecure string handling in embedded systems.
The operational impact of this vulnerability extends beyond simple service disruption to encompass potential system compromise and industrial control system (ICS) security breaches. In industrial environments where WAGO PFC 200 devices operate as critical control components, an attacker could exploit this vulnerability to execute arbitrary code on the target system, potentially gaining complete administrative control over the industrial process control functionality. The crash condition described indicates that the system becomes unstable and requires manual intervention to restore normal operations, creating potential downtime that could have significant financial and safety implications. This vulnerability particularly concerns ICS environments because it affects devices that typically operate in isolated networks but may be accessible through various attack vectors including industrial network protocols and potentially compromised remote access points. The ATT&CK framework's T1059.007 technique for command and scripting interpreter is applicable here as the vulnerability enables remote command execution capabilities through the hostname parameter manipulation.
Mitigation strategies for this vulnerability should encompass multiple layers of defense to protect industrial control systems from exploitation. Network segmentation and access control measures should be implemented to restrict direct access to the affected service ports, while regular firmware updates should be deployed to address the underlying buffer overflow condition. The recommended approach includes implementing input validation controls that enforce strict length limitations on hostname parameters and employing stack protection mechanisms such as stack canaries to detect buffer overflow attempts. Additionally, security monitoring should be enhanced to detect anomalous network traffic patterns that may indicate exploitation attempts targeting the hostname parsing functionality. Organizations should also consider implementing network-based intrusion detection systems that can identify and block malicious packets attempting to exploit this specific vulnerability. The remediation process must account for the industrial environment's operational constraints while ensuring that the firmware update process does not disrupt critical industrial operations. System administrators should also establish baseline configurations that prevent unnecessary exposure of the vulnerable service to external networks and implement proper network monitoring to detect potential exploitation attempts.