CVE-2018-13994 in FL SWITCH
Summary
by MITRE
The WebUI of PHOENIX CONTACT FL SWITCH 3xxx, 4xxx, 48xx versions 1.0 to 1.34 is vulnerable to a denial-of-service attack by making more than 120 connections.
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Analysis
by VulDB Data Team • 09/12/2023
The vulnerability identified as CVE-2018-13994 affects the web user interface of PHOENIX CONTACT FL SWITCH series devices including models 3xxx, 4xxx, and 48xx with firmware versions ranging from 1.0 to 1.34. This represents a significant security weakness that impacts industrial network infrastructure components used in manufacturing and automation environments. The affected devices are part of the FL SWITCH product line designed for industrial Ethernet switching applications where reliable network connectivity is critical for operational continuity.
The technical flaw manifests as a lack of proper connection handling mechanisms within the web interface implementation. When more than 120 concurrent connections are established to the device's web management interface, the system becomes unresponsive and enters a state where it cannot process additional requests or maintain normal operational functions. This behavior constitutes a classic denial-of-service condition where legitimate users cannot access the management interface due to resource exhaustion or improper connection management. The vulnerability operates at the application layer and specifically targets the web server component that handles HTTP requests from management interfaces.
The operational impact of this vulnerability extends beyond simple service disruption as it affects industrial control systems where network management access is essential for configuration, monitoring, and maintenance activities. In manufacturing environments, the inability to access device management interfaces can lead to extended downtime during critical maintenance windows or emergency situations where immediate configuration changes might be required. The vulnerability particularly affects environments where multiple administrators or monitoring systems might simultaneously attempt to access the device's web interface, potentially triggering the denial-of-service condition through legitimate but excessive connection attempts.
This vulnerability maps to CWE-400, which describes "Uncontrolled Resource Consumption" or "Resource Exhaustion" in software systems. The specific implementation flaw demonstrates poor resource management practices where connection limits are not properly enforced or monitored. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving service disruption and availability compromise, specifically targeting the availability aspect of the CIA triad. The attack vector requires minimal sophistication as it simply involves establishing multiple concurrent connections, making it exploitable by both automated tools and determined attackers.
Mitigation strategies should focus on implementing connection rate limiting and proper resource management within the web server implementation. Network administrators should consider implementing network segmentation to limit direct access to device management interfaces and establish proper access controls. Device firmware updates should be applied immediately to address the vulnerability, with organizations maintaining inventory tracking of all affected devices. Additionally, monitoring systems should be implemented to detect unusual connection patterns that might indicate attempts to exploit this vulnerability. Organizations should also consider implementing alternative management protocols such as SSH or SNMP for device administration to reduce reliance on the vulnerable web interface. The vulnerability highlights the importance of robust resource management in industrial network devices and the need for proper security testing during development cycles to prevent such issues from reaching production environments.