CVE-2024-21057 is a vulnerability identified in Oracle MySQL Server, specifically affecting the Server Optimizer component in versions 8.0.35 and earlier. The flaw allows an attacker with high privileges and network access via multiple protocols to cause the MySQL Server to hang or crash repeatedly, resulting in a denial-of-service (DoS) condition. The vulnerability is classified under CWE-400, which relates to uncontrolled resource consumption leading to service disruption. The CVSS 3.1 base score is 4.9, indicating a medium severity primarily due to its impact on availability (A:H), with no impact on confidentiality or integrity. Exploitation requires the attacker to have high privileges (PR:H) and network access (AV:N), but no user interaction (UI:N) is needed. The vulnerability does not escalate privileges or leak data but can disrupt database availability, potentially affecting dependent applications and services. No known exploits have been reported in the wild, but the vulnerability is considered easily exploitable given the low attack complexity (AC:L). The absence of patches at the time of reporting necessitates immediate attention to mitigate risk. This vulnerability is critical for environments where MySQL Server uptime is essential, such as enterprise applications, web services, and cloud platforms. Organizations should monitor Oracle advisories for patches and implement network-level protections to limit exposure.

For European organizations, the primary impact of CVE-2024-21057 is the potential for denial-of-service attacks against MySQL Server instances, which can disrupt business-critical applications and services relying on these databases. This can lead to operational downtime, loss of productivity, and potential financial losses, especially in sectors such as finance, healthcare, telecommunications, and government where MySQL is widely deployed. The vulnerability does not compromise data confidentiality or integrity, but the availability impact can indirectly affect service reliability and customer trust. Organizations with MySQL servers exposed to untrusted networks or with insufficient access controls are at higher risk. The disruption caused by repeated server crashes can also complicate incident response and recovery efforts. Given the medium severity and requirement for high privileges, insider threats or compromised administrative accounts pose a significant risk vector. European entities operating cloud-hosted MySQL instances or managed database services should also evaluate their exposure and coordinate with service providers to ensure timely remediation.

1. Apply official Oracle patches immediately once they become available to address CVE-2024-21057. 2. Restrict network access to MySQL Server instances using firewalls and network segmentation, allowing only trusted hosts and administrative users. 3. Enforce strict access controls and monitor privileged accounts to prevent unauthorized high-privilege access. 4. Implement robust logging and monitoring to detect unusual MySQL server behavior such as frequent crashes or hangs. 5. Consider deploying MySQL server instances behind VPNs or private networks to reduce exposure to external threats. 6. Use resource limits and query timeouts to mitigate potential resource exhaustion scenarios. 7. Regularly review and update security policies related to database administration and network access. 8. Coordinate with cloud or managed service providers to confirm patching schedules and security configurations. 9. Conduct penetration testing and vulnerability assessments focused on MySQL infrastructure to identify and remediate weaknesses. 10. Prepare incident response plans that include recovery procedures for MySQL service disruptions.