CVE-2025-54811 in OpenPLC v3
Summary
by MITRE • 10/02/2025
OpenPLC_V3 has a vulnerability in the enipThread function that occurs due to the lack of a return value. This leads to a crash when the server loop ends and execution hits an illegal ud2 instruction. This issue can be triggered remotely without authentication by starting the same server multiple times or if the server exits unexpectedly. The vulnerability allows an attacker to cause a Denial of Service (DoS) against the PLC runtime, stopping any PC started remotely without authentication. This results in the PLC process crashing and halting all automation or control logic managed by OpenPLC.
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Analysis
by VulDB Data Team • 10/02/2025
The vulnerability identified as CVE-2025-54811 resides within the OpenPLC_V3 industrial control system software, specifically within the enipThread function that handles Ethernet/IP communication protocols. This flaw represents a critical software defect that undermines the reliability and operational integrity of industrial automation systems. The vulnerability manifests when the enipThread function fails to properly return a value upon completion of its execution cycle, creating an undefined state that leads to system instability. The root cause of this issue can be traced to improper function return handling within the embedded control software architecture, which violates fundamental programming practices and security principles.
The technical exploitation of this vulnerability occurs through a specific sequence of events that begins with the initiation of multiple server instances or unexpected server termination. When the server loop concludes and execution reaches an illegal ud2 instruction, the system experiences an abrupt crash due to the missing return value causing undefined behavior. This type of vulnerability falls under CWE-754, which describes improper check for unusual or exceptional conditions in software implementations. The ud2 instruction serves as a breakpoint mechanism in x86 architecture that when executed in an improper context triggers a general protection fault, effectively crashing the entire process. The vulnerability's remote exploitability without authentication makes it particularly dangerous in industrial environments where operational technology systems are increasingly connected to corporate networks.
The operational impact of CVE-2025-54811 extends far beyond simple system instability, representing a significant threat to industrial control system availability and operational continuity. When the PLC runtime crashes due to this vulnerability, all automation and control logic managed by OpenPLC becomes inoperative, potentially leading to production halts, safety system failures, and operational disruptions in critical infrastructure environments. The DoS condition affects not just the immediate system but can cascade through interconnected processes that depend on the PLC's control functions. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks targeting industrial control systems. The attack surface is particularly concerning as it can be triggered through simple server restart operations or unexpected termination scenarios that are common in production environments.
Mitigation strategies for this vulnerability must address both the immediate software fix and broader operational security considerations. The primary remediation involves implementing proper return value handling within the enipThread function to ensure deterministic program execution and prevent undefined states. System administrators should also implement robust process monitoring and automatic restart mechanisms to minimize downtime when such crashes occur. Network segmentation and access controls should be enforced to limit the exposure of industrial control systems to unauthorized remote access attempts. Additionally, regular vulnerability assessments and penetration testing should be conducted to identify similar issues in industrial control system software. The vulnerability demonstrates the importance of following secure coding practices and adhering to industrial cybersecurity frameworks such as NIST SP 800-82 and IEC 62443 standards, which emphasize the need for robust software integrity and fault tolerance in critical infrastructure environments.