CVE-2025-21490

What it actually does

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

Why it matters to the business

Database services become unavailable, disrupting dependent applications and operations until the server is restarted; low EPSS and absence from KEV indicate limited immediate widespread risk despite the availability impact.

How an attack unfolds

An authenticated high-privileged attacker connects to the MySQL Server over supported network protocols and submits specially crafted requests that exploit the InnoDB vulnerability to force a hang or crash; no named threat actors or ransomware campaigns are associated with this issue.

How to fix it

Upgrade MySQL Server beyond the affected versions (8.0.40, 8.4.3, 9.1.0) and apply the Debian 11 package update to version 5.10.205-1 or later for all listed affected linux installations.

How to confirm the fix worked

Verify MySQL version strings post-upgrade against the fixed releases and confirm the Debian package version is at or above 5.10.205-1; test connectivity and query handling to ensure no crash occurs under privileged access.

Typical attack path

1. Obtain high-privileged network credentials for the MySQL Server
2. Establish a connection using one of the multiple supported protocols
3. Transmit crafted queries or packets targeting the InnoDB component
4. Induce repeated server hang or crash to achieve denial of service

How to detect it

Inspect MySQL error logs and system logs for repeated InnoDB-related crashes or hangs following high-privileged connections; correlate with authentication events from network protocols.

What your security team should do

• Prioritize patching MySQL instances on Debian 11 to the specified fixed package version
• Review and restrict high-privileged network access to MySQL where possible
• Monitor EPSS trend (stable at ~0.0128) and re-evaluate if new exploit maturity emerges