CVE-2019-5077 in PFC100
Summary
by MITRE
An exploitable denial-of-service vulnerability exists in the iocheckd service ??I/O-Chec?? functionality of WAGO PFC 200 Firmware versions 03.01.07(13) and 03.00.39(12), and WAGO PFC 100 Firmware version 03.00.39(12). A specially crafted set of packets can cause a denial of service, resulting in the device entering an error state where it ceases all network communications. An attacker can send unauthenticated packets to trigger this vulnerability.
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Analysis
by VulDB Data Team • 03/15/2024
The vulnerability identified as CVE-2019-5077 represents a critical denial-of-service weakness within the iocheckd service of WAGO PFC 200 and PFC 100 industrial control devices. This flaw manifests specifically within the I/O-Check functionality, which is designed to monitor and validate input/output operations in industrial automation environments. The affected firmware versions 03.01.07(13), 03.00.39(12) for PFC 200 models and 03.00.39(12) for PFC 100 devices all share this common vulnerability that compromises system availability. The root cause lies in insufficient input validation mechanisms within the iocheckd service, which fails to properly sanitize incoming network packets before processing them. This weakness creates an exploitable condition where maliciously crafted packets can cause the service to crash or enter an unstable error state, ultimately leading to complete network communication failure across the affected device.
The technical exploitation of this vulnerability occurs through the transmission of specially crafted packets to the iocheckd service without requiring authentication credentials, making it particularly dangerous in industrial network environments where physical access controls may be limited. When the vulnerable service receives these malformed packets, it processes them without adequate validation, leading to a memory corruption or resource exhaustion condition that causes the service to terminate unexpectedly. The resulting error state prevents the device from maintaining its network connectivity, effectively rendering it non-functional within the industrial control network. This behavior aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a classic example of improper input validation that can lead to service disruption. The vulnerability's impact is particularly severe in industrial settings where continuous operation is critical for process control and safety systems.
The operational consequences of CVE-2019-5077 extend beyond simple service interruption to potentially compromise entire industrial control processes that depend on these devices. When the iocheckd service fails, the device ceases all network communications, creating a cascading effect that can disrupt automation workflows and process monitoring systems. In industrial environments, this vulnerability can lead to production halts, safety system failures, and increased maintenance costs as operators must manually restart affected devices. The unauthenticated nature of the attack means that even limited network access can be exploited, making this vulnerability particularly attractive to threat actors targeting industrial control systems. This weakness falls under the ATT&CK technique T1499.002 for network denial of service, which specifically addresses attacks targeting network infrastructure and services. The vulnerability's impact is amplified in environments where these devices operate as part of critical infrastructure, where the loss of network connectivity can have far-reaching operational consequences.
Mitigation strategies for CVE-2019-5077 should focus on immediate firmware updates provided by WAGO to address the input validation flaws in the iocheckd service. Organizations must also implement network segmentation and access controls to limit exposure of these devices to untrusted networks, particularly in industrial environments where physical security measures may be insufficient. Network monitoring solutions should be deployed to detect unusual traffic patterns that might indicate exploitation attempts, while regular vulnerability assessments should be conducted to identify other potentially vulnerable services within the industrial control network. The implementation of network access control lists and firewall rules can help restrict access to the specific ports used by the iocheckd service, reducing the attack surface. Additionally, industrial security frameworks such as ICS-CERT recommendations should be followed to establish comprehensive security postures that address both known vulnerabilities and emerging threats in industrial control systems. Organizations should also consider implementing intrusion detection systems specifically tuned to detect the signature patterns associated with this vulnerability to enable rapid response to exploitation attempts.