CVE-2025-21529

What it actually does

The flaw in the Information Schema component permits a high-privileged network attacker to submit queries that trigger a hang or repeatable crash, resulting in complete denial of service against the MySQL Server process.

Why it matters to the business

Successful exploitation causes unplanned database outages that interrupt dependent applications and services, leading to operational downtime and potential data access loss until the server is restarted.

How an attack unfolds

An attacker with high database privileges obtains network access and issues specially crafted queries against Information Schema tables, exploiting insufficient input validation to force the server into a hung or crashed state.

How to fix it

Upgrade affected MySQL Server installations to the latest patched releases beyond 8.0.40, 8.4.3, and 9.1.0 respectively. Apply vendor security updates as soon as they become available and restrict unnecessary high-privileged network access.

How to confirm the fix worked

Confirm the running MySQL version is newer than the listed affected releases, review release notes for the specific fix, and test that Information Schema queries no longer produce crashes under equivalent privilege levels.

Typical attack path

1. Obtain high-privileged database credentials
2. Establish network connection to MySQL using supported protocols
3. Issue crafted queries targeting Information Schema views
4. Trigger repeated crashes or hangs to sustain denial of service

How to detect it

Review MySQL error logs and general query logs for repeated crashes or hangs correlated with Information Schema access by high-privileged accounts; look for abrupt server restarts without external cause.

What your security team should do

• Prioritize patching all MySQL instances to fixed versions within standard change windows
• Reduce the number of accounts with high privileges and network access
• Monitor for unusual query patterns against Information Schema in database logs
• Validate backup and recovery procedures to minimize downtime from DoS events