A vulnerability in Oracle MySQL Server (CVE-2025-21494) affects versions 8.0.39 and prior, 8.4.2 and prior, and 9.0.1 and prior. It allows a high privileged attacker with logon access to cause a denial of service by hanging or crashing the MySQL Server. The vulnerability is difficult to exploit and impacts availability without compromising confidentiality or integrity. The CVSS 3.1 base score is 4.1, indicating medium severity.