CVE-2022-21155 in SCADA Server
Summary
by MITRE • 04/12/2022
A specially crafted packet sent to the Fernhill SCADA Server Version 3.77 and earlier may cause an exception, causing the server process (FHSvrService.exe) to exit.
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Analysis
by VulDB Data Team • 04/12/2022
This vulnerability represents a critical denial of service condition affecting Fernhill SCADA Server versions 3.77 and earlier, where malformed network packets can trigger unhandled exceptions within the core server process. The affected component FHSvrService.exe demonstrates inadequate input validation mechanisms that fail to properly handle crafted packet structures, leading to abrupt process termination and complete service disruption. Such vulnerabilities in industrial control systems pose significant operational risks as they can be exploited by malicious actors to disrupt critical infrastructure operations without requiring elevated privileges or specialized access.
The technical flaw manifests through insufficient sanitization of incoming network traffic, specifically targeting the server's packet processing routines that lack proper exception handling for malformed data structures. When a specially crafted packet is received, it likely contains unexpected byte sequences or protocol violations that cause the application to throw an uncaught exception, resulting in the immediate termination of the FHSvrService.exe process. This behavior aligns with common software vulnerabilities categorized under CWE-248, which addresses "Exception Handling" issues where programs fail to properly handle exceptional conditions and terminate unexpectedly.
The operational impact of this vulnerability extends beyond simple service interruption, as it can compromise the availability of critical industrial processes managed by the SCADA system. In environments where continuous operation is essential for safety and production purposes, such a disruption could lead to cascading failures in manufacturing processes, power grid management, or other infrastructure systems that rely on stable communication between control components. The vulnerability's exploitability is particularly concerning given that it requires no authentication or specialized knowledge beyond basic network packet crafting techniques.
Organizations operating affected SCADA systems should prioritize immediate remediation through official vendor patches or firmware updates, as the vulnerability exists in multiple versions of the software and affects critical infrastructure operations. Additionally, network segmentation strategies should be implemented to limit exposure, including firewall rules that restrict access to the affected server from untrusted networks, and monitoring systems should be deployed to detect abnormal packet patterns that might indicate exploitation attempts. Security professionals should also consider implementing intrusion detection systems specifically designed for industrial control system protocols to identify potential exploitation activities targeting these types of vulnerabilities.
This vulnerability exemplifies the broader challenges faced in securing industrial control systems where legacy software components often lack modern security design principles and comprehensive testing for edge cases in network communication. The exploitation patterns align with tactics described in the attack framework under the MITRE ATT&CK matrix, particularly within the execution and privilege escalation domains where initial access may be achieved through network-based attacks that leverage software vulnerabilities to achieve system compromise or disruption.
Organizations should conduct thorough vulnerability assessments of their entire industrial control system infrastructure to identify similar issues in other components that might exhibit comparable behaviors. The remediation process must include comprehensive testing of patched software in controlled environments before deployment to production systems, given the critical nature of these operations and the potential for unintended side effects from security updates in operational technology environments.