CVE-2025-21534

What it actually does

High-privileged network attacker can trigger a hang or repeatable crash in the Performance Schema component, resulting in complete denial of service for the MySQL Server process.

Why it matters to the business

Database service becomes unavailable, interrupting applications and operations that depend on it; high-privilege requirement limits likelihood but impact is severe for availability.

How an attack unfolds

An attacker with high privileges and network access sends specially crafted requests over supported protocols to the Performance Schema, causing the server to hang or crash repeatedly.

How to fix it

Upgrade affected MySQL Server installations to the latest fixed versions beyond 8.0.39, 8.4.2, and 9.0.1. For listed php packages apply the referenced Ubuntu updates: php7.4 to 7.4.3-4ubuntu2.23 and php8.1 to 8.1.2-1ubuntu2.18.

How to confirm the fix worked

Confirm MySQL Server version is newer than the affected ranges and test that Performance Schema operations no longer produce crashes under load from privileged accounts.

Typical attack path

1. Obtain high-privileged database credentials
2. Establish network connection to the MySQL server using supported protocols
3. Send crafted requests targeting the Performance Schema component
4. Trigger repeated crashes or hangs resulting in denial of service

How to detect it

Review database error logs, crash dumps, and performance schema telemetry for repeated hangs or abrupt terminations originating from privileged network sessions.

What your security team should do

• Apply the appropriate MySQL or php package updates immediately given the published date and stable EPSS
• Restrict network access to the database to only trusted sources
• Review and minimize the number of high-privileged accounts with network access
• Monitor for availability anomalies in database performance metrics