CVE-2020-8867 in OPC Foundation UA .NET Standard
Summary
by MITRE
This vulnerability allows remote attackers to create a denial-of-service condition on affected installations of OPC Foundation UA .NET Standard 1.04.358.30. Authentication is not required to exploit this vulnerability. The specific flaw exists within the handling of sessions. The issue results from the lack of proper locking when performing operations on an object. An attacker can leverage this vulnerability to create a denial-of-service condition against the application. Was ZDI-CAN-10295.
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Analysis
by VulDB Data Team • 06/02/2024
The vulnerability described in CVE-2020-8867 represents a critical denial-of-service weakness within the OPC Foundation UA .NET Standard 1.04.358.30 implementation that affects industrial automation and control systems. This flaw specifically targets the session management component of the OPC UA stack, which is fundamental to establishing and maintaining secure communication between industrial devices and supervisory systems. The vulnerability's severity is amplified by its accessibility since no authentication is required for exploitation, making it particularly dangerous in operational technology environments where systems may be exposed to untrusted networks.
The technical root cause of this vulnerability stems from inadequate thread synchronization mechanisms within the session handling code. When multiple concurrent operations attempt to access and modify shared session objects without proper locking mechanisms, race conditions can occur that lead to inconsistent object states and potential application crashes. This flaw falls under the CWE-362 category of "Concurrent Execution using Shared Resource with Improper Synchronization" which is a well-established class of vulnerabilities that can lead to unpredictable behavior in multi-threaded applications. The lack of proper locking allows simultaneous access to critical session data structures, causing memory corruption or invalid state transitions that ultimately result in application instability.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the integrity of industrial control systems that rely on OPC UA for communication. In manufacturing environments, the denial-of-service condition could lead to production halts, sensor data loss, or complete system unavailability during critical operations. The vulnerability affects systems where OPC UA servers are deployed, particularly those implementing the .NET Standard stack, which is commonly used in industrial automation scenarios including process control, asset management, and SCADA systems. Attackers can exploit this weakness by simply connecting to the affected OPC UA server and initiating multiple concurrent session operations, causing the server to become unresponsive and requiring manual intervention to restore service.
Organizations should implement immediate mitigations including applying the vendor-provided patches or updates that address the thread synchronization issues in the session handling code. Network segmentation and access control measures can help reduce the attack surface by limiting exposure of OPC UA servers to untrusted networks. Monitoring systems should be configured to detect unusual session activity patterns that might indicate exploitation attempts. The vulnerability's characteristics align with ATT&CK technique T1499.004 which covers "Network Denial of Service" and represents a significant risk to industrial cybersecurity posture. Additionally, implementing proper input validation and session management controls can help prevent similar issues from occurring in other components of the industrial control system architecture. Organizations should also consider conducting thorough vulnerability assessments of their entire OPC UA deployment to identify any additional instances of improper synchronization mechanisms that could lead to similar denial-of-service conditions.