CVE-2025-30687 is a vulnerability identified in Oracle MySQL Server's Optimizer component affecting multiple supported versions: 8.0.0 through 8.0.41, 8.4.0 through 8.4.4, and 9.0.0 through 9.2.0. The flaw allows an attacker with low privileges and network access via multiple protocols to cause the MySQL Server to hang or crash repeatedly, resulting in a complete denial of service (DoS). The CVSS 3.1 base score is 6.5, reflecting a medium severity primarily due to the impact on availability (A:H) while confidentiality and integrity remain unaffected. The attack vector is network-based (AV:N), requires low attack complexity (AC:L), and low privileges (PR:L), with no user interaction (UI:N) needed. The vulnerability is classified under CWE-732, which relates to incorrect permission assignment or management, indicating that the issue likely stems from improper handling of privileges or access controls within the optimizer component. Although no exploits have been observed in the wild, the vulnerability is easily exploitable given the low privilege and network access requirements. The absence of patch links suggests that Oracle has not yet released a fix, emphasizing the need for interim mitigations. The vulnerability could be triggered remotely, potentially affecting any MySQL Server instance exposed to untrusted networks or insufficiently protected internal networks. This could disrupt database availability, impacting applications and services dependent on MySQL, especially in environments where high availability is critical.

For European organizations, the primary impact of CVE-2025-30687 is on the availability of MySQL Server instances, which could lead to significant service disruptions. Many enterprises, government agencies, and service providers across Europe rely on MySQL for critical data storage and application backends. A successful denial of service attack could halt business operations, degrade customer experience, and cause financial losses. Sectors such as finance, healthcare, telecommunications, and public administration are particularly vulnerable due to their reliance on continuous database availability. Additionally, organizations with MySQL servers exposed to the internet or accessible across less secure internal networks face higher risk. The lack of impact on confidentiality and integrity reduces the risk of data breaches but does not diminish the operational consequences of downtime. Furthermore, repeated crashes could increase recovery time and operational costs. The medium severity rating suggests a moderate but tangible threat level that requires attention to maintain service continuity and compliance with European data protection and operational standards.

1. Immediately audit all MySQL Server instances to identify affected versions (8.0.0-8.0.41, 8.4.0-8.4.4, 9.0.0-9.2.0) and isolate those exposed to untrusted networks. 2. Implement strict network segmentation and firewall rules to restrict access to MySQL servers only to trusted hosts and services. 3. Enforce the principle of least privilege by reviewing and tightening MySQL user permissions, ensuring that low privileged accounts cannot exploit this vulnerability. 4. Monitor MySQL server logs and network traffic for unusual patterns indicative of attempted exploitation, such as repeated connection attempts or server hangs. 5. Prepare for rapid deployment of patches or updates once Oracle releases a fix; subscribe to Oracle security advisories for timely notifications. 6. Consider deploying Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) with custom rules to detect and block exploit attempts targeting this vulnerability. 7. Develop and test incident response plans to quickly recover MySQL services in case of denial of service attacks. 8. Where feasible, implement redundancy and failover mechanisms to minimize downtime impact. 9. Educate database administrators and security teams about this vulnerability and recommended defensive measures.