CVE-2026-34303 Denial of service in MySQL Server

Medium 6.5 Published 21 Apr 2026 Updated 22 Apr 2026

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: Available

What is CVE-2026-34303?

CVE-2026-34303 is a medium-severity denial of service vulnerability in Oracle Mysql Server, published on 21 Apr 2026. 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 8.0.0-8.0.45, 8.4.0-8.4.8 and 9.0.0-9.6.0. 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-400

Which versions are affected by CVE-2026-34303?

It affects 1 product.

Products include Oracle Mysql Server.

How do I fix CVE-2026-34303?

Apply the vendor's patch.

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-2026-34303 being exploited?

There is no known exploitation of CVE-2026-34303 in the wild and no public exploit code.

All Oracle Mysql Server vulnerabilities

Sources

Also known as AZL-83151, BELL-CVE-2026-34303, DEBIAN-CVE-2026-34303, ECHO-5ab2-a471-3625, GHSA-565v-jcgw-g7vh, MINI-2cv9-462j-3f36 and 6 more.