CVE-2025-30689

What it actually does

The flaw in the Server: Optimizer component permits a high-privileged network attacker to trigger a hang or repeatable crash, resulting in complete denial of service to the MySQL Server process.

Why it matters to the business

Database services become unavailable, interrupting applications, analytics workloads, and any operations that rely on the affected MySQL instances until the server is restarted or recovered.

How an attack unfolds

An attacker with high-privileged network credentials connects to the MySQL server over supported protocols and submits crafted queries that exercise the vulnerable optimizer code path, causing the server to hang or crash.

How to fix it

Apply the latest MySQL patch releases that resolve the optimizer issue for the affected branches (8.0.42+, 8.4.5+, 9.2.1+). Validate the upgrade in a non-production environment before rolling out to production instances.

How to confirm the fix worked

Confirm the running MySQL version is no longer within the vulnerable ranges listed in the advisory; test that previously crashing queries no longer cause a server crash or hang.

Typical attack path

1. Obtain high-privileged MySQL credentials with network access
2. Connect to the target MySQL instance using a supported protocol
3. Issue specially crafted queries that trigger the optimizer flaw
4. Observe server hang or crash, confirming denial of service

How to detect it

Review MySQL error logs and process crash dumps for optimizer-related assertion failures or abrupt terminations around the time of suspected incidents; correlate with authentication events from privileged accounts.

What your security team should do

• Prioritize patching all internet-facing or high-value MySQL instances within the next maintenance window
• Review and restrict high-privileged accounts that have network access to only necessary hosts
• Monitor EPSS score and any new exploit publications for changes in risk posture