CVE-2023-5676 is a race condition vulnerability categorized under CWE-364, affecting the Eclipse Foundation's OpenJ9 Java Virtual Machine versions prior to 0.41.0. The issue arises during the JVM startup phase when the process receives shutdown signals such as SIGTERM, SIGINT, or SIGHUP before the JVM has fully initialized. Under these conditions, the JVM's signal handler can enter an infinite busy wait on a spinlock, effectively causing a hang, or it may crash with a segmentation fault. This behavior results from improper synchronization in signal handling code, where the JVM is not prepared to handle termination signals during early initialization. The vulnerability impacts the availability of the JVM process, potentially causing denial of service (DoS) conditions. Exploitation requires local access with high privileges to send signals to the JVM process, and no user interaction is needed. There are no known exploits in the wild, and no patches have been linked yet, although upgrading to version 0.41.0 or later is expected to resolve the issue. The CVSS v3.1 score is 4.1, reflecting a medium severity due to the limited attack vector (local), high attack complexity, and the impact confined to availability without affecting confidentiality or integrity.

For European organizations, the primary impact of CVE-2023-5676 is on service availability. Systems running Java applications on OpenJ9 JVM versions before 0.41.0 may experience unexpected hangs or crashes if shutdown signals are sent during JVM startup. This can lead to denial of service conditions affecting critical business applications, especially in environments where JVM startup and shutdown are frequent or automated. Industries relying on Java for backend services, financial systems, or enterprise applications could face operational disruptions. Since exploitation requires local high-privilege access, the risk from remote attackers is low, but insider threats or compromised internal systems could trigger the vulnerability. The lack of impact on confidentiality and integrity limits the risk to data breaches or unauthorized data modification. However, availability issues in production environments can cause significant downtime and financial loss. European organizations with strict uptime requirements or regulatory obligations to maintain service continuity should prioritize addressing this vulnerability.

To mitigate CVE-2023-5676, organizations should upgrade OpenJ9 JVM to version 0.41.0 or later as soon as the patch is available. Until then, operational procedures should be adjusted to avoid sending shutdown signals (SIGTERM, SIGINT, SIGHUP) to the JVM process during its initialization phase. Monitoring and controlling process signals in automated deployment or orchestration systems can help prevent accidental triggering. Additionally, restricting local access to JVM host systems and limiting high-privilege user capabilities reduces the risk of exploitation. Implementing robust logging and alerting for JVM crashes or hangs can facilitate rapid detection and response. For environments where upgrading is delayed, consider isolating critical JVM instances or using alternative JVM implementations temporarily. Finally, coordinate with development and operations teams to ensure JVM lifecycle management accounts for this vulnerability.