CVE-2023-28831 is an integer overflow vulnerability classified under CWE-190 found in the OPC UA (Open Platform Communications Unified Architecture) implementations written in ANSI C and C++ within Siemens SIMATIC BRAUMAT products. The vulnerability manifests during the certificate validation process, where an integer overflow or wraparound causes the application to enter an infinite loop. This infinite loop effectively results in a denial of service (DoS) condition, as the application becomes unresponsive or stuck processing the malicious certificate. The flaw can be triggered remotely by an unauthenticated attacker who sends a specially crafted certificate to the affected OPC UA service. The vulnerability does not require any privileges or user interaction, making it easier to exploit. The CVSS v3.1 base score is 7.5, indicating high severity, with the vector AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, meaning network attack vector, low attack complexity, no privileges or user interaction required, unchanged scope, no impact on confidentiality or integrity, but high impact on availability. Siemens SIMATIC BRAUMAT is an industrial automation system used primarily in process industries such as brewing and beverage production, where OPC UA is used for secure communication. The vulnerability could disrupt industrial processes by causing system downtime or degraded performance. No patches or exploits are currently publicly available, but the risk remains significant due to the critical nature of the affected systems.

The primary impact of CVE-2023-28831 is a denial of service condition that affects the availability of Siemens SIMATIC BRAUMAT systems. For European organizations, especially those in manufacturing, utilities, and critical infrastructure sectors that rely on Siemens automation products, this could lead to operational disruptions, production downtime, and potential safety risks. The inability to validate certificates properly may also undermine trust in secure communications within industrial networks. Since the vulnerability can be exploited remotely without authentication, attackers could target exposed OPC UA endpoints to cause service outages. This could have cascading effects on supply chains and industrial processes. Although confidentiality and integrity are not directly impacted, the loss of availability in critical control systems can have severe economic and safety consequences. The lack of known exploits in the wild suggests limited current exploitation, but the vulnerability remains a significant risk until mitigated.

1. Monitor Siemens advisories closely and apply official patches or updates for SIMATIC BRAUMAT as soon as they become available. 2. Restrict network access to OPC UA services by implementing strict firewall rules and network segmentation to limit exposure to untrusted networks. 3. Employ intrusion detection and prevention systems (IDS/IPS) to monitor and block suspicious certificate validation traffic targeting OPC UA endpoints. 4. Conduct regular security assessments and penetration testing focused on industrial control systems to identify exposure and weaknesses. 5. Implement certificate validation policies that include sanity checks or rate limiting to prevent infinite loops or resource exhaustion. 6. Where possible, disable or restrict OPC UA certificate validation on non-critical systems or isolate these systems from external networks. 7. Maintain up-to-date asset inventories to identify all instances of SIMATIC BRAUMAT and OPC UA implementations for targeted mitigation. 8. Train operational technology (OT) staff on recognizing and responding to denial of service incidents related to certificate validation issues.