CVE-2025-21566 Denial of service in MySQL Server

Medium 6.5 Published 21 Jan 2025 Updated 3 Nov 2025

A low-privileged attacker can cause a complete denial of service in MySQL Server via the Optimizer component.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2025-21566?

CVE-2025-21566 is a medium-severity denial of service vulnerability in Oracle Mysql Server, published on 21 Jan 2025. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 9.1.0 and prior. Easily exploitable vulnerability allows low privileged attacker with network access via multiple protocols to compromise MySQL Server. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of MySQL Server. CVSS 3.1 Base Score 6.5 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).

Weakness: CWE-732

Which versions are affected by CVE-2025-21566?

It affects 1 product.

Products include Oracle Mysql Server.

How do I fix CVE-2025-21566?

No fix has been published for CVE-2025-21566 yet. Limit exposure of the affected software until one is available.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2025-21566 being exploited?

There is no known exploitation of CVE-2025-21566 in the wild and no public exploit code.

All Oracle Mysql Server vulnerabilities

Sources

Also known as GHSA-4x4h-rvfw-x95m, MINI-c6mw-fg2h-g2rx, UBUNTU-CVE-2025-21566.