CVE-2024-21171 is a vulnerability identified in the Oracle MySQL Server product, specifically within the Server Optimizer component. It affects all supported versions up to 8.0.37 and 8.4.0. The vulnerability allows an attacker with low privileges and network access through multiple protocols to cause the MySQL Server to hang or crash repeatedly, resulting in a complete denial-of-service (DoS) condition. The CVSS 3.1 base score is 6.5, reflecting a medium severity primarily due to its impact on availability (A:H) without affecting confidentiality or integrity. The attack vector is network-based (AV:N), requiring low attack complexity (AC:L) and low privileges (PR:L), with no user interaction (UI:N) needed. The vulnerability is classified under CWE-400, indicating a resource exhaustion or DoS issue. While no exploits are currently known in the wild, the ease of exploitation and the critical role of MySQL in many infrastructures make this a significant concern. The absence of patches at the time of reporting necessitates immediate defensive measures to reduce exposure. The vulnerability could be triggered via multiple network protocols supported by MySQL, increasing the attack surface. This flaw could disrupt database availability, affecting applications and services dependent on MySQL databases.

For European organizations, the primary impact of CVE-2024-21171 is the potential for service disruption due to denial-of-service attacks against MySQL Server instances. This can lead to downtime of critical applications relying on MySQL databases, affecting sectors such as finance, telecommunications, healthcare, and government services where database availability is crucial. The inability to maintain database uptime could result in operational delays, loss of customer trust, and financial losses. Since the vulnerability does not compromise data confidentiality or integrity, the risk of data breaches is low; however, the availability impact alone can severely affect business continuity. Organizations with distributed MySQL deployments or those exposed to public networks are at higher risk. Additionally, repeated crashes could complicate recovery efforts and increase administrative overhead. The medium severity rating suggests that while the threat is significant, it is not catastrophic, but still demands timely attention to avoid exploitation. European entities with compliance obligations around service availability (e.g., financial institutions under PSD2 or critical infrastructure under NIS2) may face regulatory scrutiny if disruptions occur.

1. Implement strict network segmentation and firewall rules to limit MySQL Server access only to trusted hosts and networks, minimizing exposure to potential attackers. 2. Monitor MySQL server logs and system metrics for unusual patterns such as frequent crashes, hangs, or resource exhaustion symptoms indicative of exploitation attempts. 3. Employ rate limiting and connection throttling on MySQL ports to reduce the risk of resource exhaustion attacks. 4. Use intrusion detection/prevention systems (IDS/IPS) tuned to detect anomalous MySQL traffic or known attack signatures once available. 5. Regularly update and patch MySQL Server as soon as Oracle releases a security fix for CVE-2024-21171. 6. Consider deploying high-availability MySQL clusters or failover mechanisms to maintain service continuity during potential DoS events. 7. Restrict MySQL user privileges to the minimum necessary to reduce the impact scope if an attacker gains low-level access. 8. Conduct vulnerability scanning and penetration testing focused on MySQL services to identify exposure and validate defenses. 9. Educate network and database administrators about this vulnerability and encourage proactive monitoring and incident response planning. 10. Evaluate alternative database solutions or cloud-managed services with built-in protections if risk tolerance is low.