CVE-2024-21135 is a vulnerability in the Oracle MySQL Server, specifically within the Server Optimizer component, affecting versions 8.0.36 and earlier, as well as 8.3.0 and earlier. The flaw allows a high privileged attacker who has network access via multiple protocols to cause the MySQL Server to hang or crash repeatedly, resulting in a complete denial of service (DoS). The vulnerability does not affect the confidentiality or integrity of the data but impacts availability significantly. The CVSS 3.1 base score is 4.9, with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), requiring high privileges (PR:H), no user interaction (UI:N), unchanged scope (S:U), and impact limited to availability (A:H). This means an attacker must already have high-level access to the MySQL Server environment and network access to exploit the vulnerability. The absence of known exploits in the wild suggests that exploitation is not widespread yet, but the ease of causing DoS conditions makes it a concern for service reliability. The vulnerability affects multiple protocols, increasing the attack surface. Since MySQL is widely used for database management in enterprise environments, this vulnerability could disrupt critical business operations if exploited. Oracle has published the vulnerability details but no direct patch links were provided in the source information, indicating organizations should monitor Oracle advisories for updates.

For European organizations, the primary impact of CVE-2024-21135 is the potential for denial of service on MySQL Server instances, which can disrupt business-critical applications relying on database availability. This can lead to operational downtime, loss of productivity, and potential financial losses. Industries such as finance, telecommunications, healthcare, and e-commerce, which heavily depend on MySQL databases, are particularly at risk. The requirement for high privileges limits the risk to insiders or attackers who have already compromised internal systems, but the network accessibility via multiple protocols broadens the potential attack vectors. Given the interconnected nature of European IT infrastructure, a successful DoS attack could cascade, affecting service providers and customers. Additionally, regulatory frameworks like GDPR emphasize service availability as part of data protection, so prolonged outages could have compliance implications. Organizations with remote or cloud-hosted MySQL deployments may face increased exposure if network controls are insufficient.

1. Apply patches promptly once Oracle releases official fixes for the affected MySQL Server versions. 2. Restrict network access to MySQL Server instances by implementing strict firewall rules and network segmentation, allowing only trusted hosts and protocols. 3. Limit high privilege accounts and enforce the principle of least privilege to reduce the risk of insider threats or lateral movement by attackers. 4. Monitor MySQL Server logs and network traffic for unusual activity or repeated connection attempts that could indicate exploitation attempts. 5. Employ intrusion detection and prevention systems (IDS/IPS) tuned to detect anomalies in MySQL traffic patterns. 6. Consider deploying MySQL in high availability or failover configurations to minimize downtime in case of DoS attacks. 7. Regularly review and update security policies related to database access and network exposure. 8. Conduct internal security audits and penetration testing focusing on privilege escalation and network access controls around MySQL infrastructure.