CVE-2024-20921 is a vulnerability in Oracle Java SE, Oracle GraalVM for JDK, and Oracle GraalVM Enterprise Edition affecting specific versions. It involves the Hotspot component and allows a difficult-to-exploit attack by unauthenticated network attackers via multiple protocols. Successful exploitation can lead to unauthorized access to critical or all accessible data. The vulnerability impacts confidentiality but not integrity or availability. It also affects sandboxed Java Web Start applications or applets that run untrusted code relying on the Java sandbox. The CVSS 3.1 base score is 5.9, indicating medium severity.