A vulnerability in Oracle MySQL Server (CVE-2025-21505) affects versions 8.0.40 and prior, 8.4.3 and prior, and 9.1.0 and prior. It allows a high-privileged attacker with network access via multiple protocols to cause a denial of service by hanging or crashing the MySQL Server. The CVSS 3.1 base score is 4.9, indicating a medium severity impact focused on availability.