CVE-2026-67859 in open62541
Summary
by MITRE • 08/05/2026
Buffer Overflow vulnerability in open62541 v1.5.5 allows a remote attacker to cause a denial of service via the Discovery/LDS handling.
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Analysis
by VulDB Data Team • 08/05/2026
The buffer overflow vulnerability in open62541 version 1.5.5 represents a critical security flaw that specifically affects the Discovery and LDS (Local Discovery Server) handling components of this widely-used OPC UA stack implementation. This vulnerability arises from improper input validation and memory management within the server's discovery protocol processing logic, creating an exploitable condition that can be triggered by remote attackers without authentication requirements. The affected software serves as a fundamental component in industrial automation systems, making this vulnerability particularly concerning for operational technology environments where reliability and security are paramount.
The technical implementation flaw occurs when the open62541 server processes incoming discovery requests or LDS communications, specifically during the parsing and handling of network packets containing malformed or excessively large data structures. The vulnerability manifests as a classic buffer overflow condition where insufficient bounds checking allows an attacker to write beyond allocated memory boundaries in the server's memory space. This occurs when processing certain OPC UA discovery messages that contain oversized arrays, strings, or other structured data elements that exceed the expected buffer capacity during deserialization operations. According to CWE-121, this vulnerability maps directly to improper boundary checking in heap-based buffers, while the ATT&CK framework categorizes it under T1499.004 for network denial of service attacks targeting industrial control systems.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire industrial control networks where open62541 is deployed as a core communication component. Remote attackers can leverage this condition to cause immediate server crashes, leading to denial of service that can disrupt critical manufacturing processes, data acquisition systems, or monitoring infrastructure. In environments where OPC UA servers are used for real-time process control, such an attack could result in production halts, safety system failures, or data integrity issues that may require extensive recovery procedures. The vulnerability affects the server's ability to maintain stable connections with clients and other discovery servers, potentially leading to cascading failures across interconnected systems. Organizations using this software in critical infrastructure contexts face heightened risk of operational disruption and potential safety implications.
Mitigation strategies for this buffer overflow vulnerability should prioritize immediate patching of open62541 to version 1.5.6 or later where the issue has been addressed through proper input validation and memory boundary checks. Network segmentation and access controls should be implemented to limit exposure of OPC UA services to untrusted networks, while monitoring systems should be deployed to detect unusual discovery traffic patterns that might indicate exploitation attempts. Security teams should implement robust network intrusion detection rules specifically targeting OPC UA protocol anomalies related to discovery operations and consider deploying application firewalls or deep packet inspection mechanisms to filter malicious discovery requests before they reach vulnerable server instances. Organizations utilizing older versions of the software should conduct comprehensive vulnerability assessments of their industrial control networks to identify all potentially affected systems and develop incident response procedures for handling potential exploitation attempts. The fix typically involves implementing proper bounds checking in the deserialization logic and ensuring that all incoming data structures are validated against expected size parameters before memory allocation occurs, addressing the underlying CWE-121 classification through defensive programming practices.