CVE-2025-21522 is a vulnerability in the Oracle MySQL Server's Parser component affecting multiple supported versions up to 8.0.40, 8.4.3, and 9.1.0. The flaw allows an attacker with low privileges and network access via multiple protocols to exploit the server, causing it to hang or crash repeatedly, resulting in a complete denial-of-service (DoS). The vulnerability is classified under CWE-770, which relates to allocation of resources without limits or throttling, leading to resource exhaustion. The CVSS 3.1 base score is 6.5, reflecting a medium severity primarily due to the impact on availability (A:H) without affecting confidentiality or integrity. The attack vector is network-based (AV:N), requires low attack complexity (AC:L), and low privileges (PR:L), with no user interaction needed (UI:N). The scope remains unchanged (S:U), meaning the vulnerability affects only the vulnerable component without impacting other system components. No patches or exploits are currently publicly available, but the vulnerability is easily exploitable due to the low privilege and network access requirements. The vulnerability can be triggered via multiple protocols supported by MySQL Server, increasing the attack surface. This makes it a significant concern for environments where MySQL Server is exposed to untrusted networks or where attackers can gain low-level access. The vulnerability could be leveraged to disrupt database availability, impacting dependent applications and services.

For European organizations, this vulnerability poses a risk of service disruption due to MySQL Server crashes or hangs, leading to denial-of-service conditions. Organizations relying heavily on MySQL for critical business applications, including e-commerce, finance, healthcare, and public services, could experience operational downtime, loss of productivity, and potential reputational damage. While no data confidentiality or integrity loss is indicated, availability impacts can indirectly affect business continuity and customer trust. The ease of exploitation with low privileges and network access means that attackers who gain minimal access to internal or exposed networks could trigger the DoS. This is particularly concerning for organizations with insufficient network segmentation or exposed MySQL instances. Additionally, the lack of user interaction requirement facilitates automated exploitation attempts. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, especially as exploit code may emerge following public disclosure. Organizations in sectors with high regulatory scrutiny in Europe may also face compliance risks if service disruptions affect critical infrastructure or data processing obligations.

1. Monitor Oracle's official channels for patches addressing CVE-2025-21522 and apply them promptly once released. 2. Restrict network access to MySQL Server instances by implementing strict firewall rules and network segmentation, limiting exposure to trusted hosts only. 3. Disable or restrict unused MySQL protocols and services to reduce the attack surface. 4. Implement robust monitoring and alerting for unusual MySQL server behavior, such as frequent crashes, hangs, or resource exhaustion symptoms. 5. Employ rate limiting and connection throttling mechanisms at the network or application layer to mitigate potential resource exhaustion attacks. 6. Review and minimize privileges for MySQL users and service accounts to reduce the risk of exploitation by low-privileged attackers. 7. Conduct regular security assessments and penetration tests focusing on database infrastructure to identify and remediate potential weaknesses. 8. Consider deploying high-availability and failover solutions to maintain service continuity in case of DoS events. 9. Educate IT and security teams about this vulnerability to ensure rapid detection and response. 10. Use network intrusion detection systems (NIDS) to detect anomalous traffic patterns targeting MySQL services.