In July 2023, Oracle disclosed a vulnerability in MySQL Server, specifically targeting the InnoDB storage engine. Cataloged as CVE-2023-22066, this flaw allows a high-privileged attacker to crash the MySQL service, resulting in a Denial-of-Service (DoS) condition. In this article, we'll break down how CVE-2023-22066 works, the impact, and provide an easy-to-follow reproduction scenario—demonstrating why patching is critical for any organization using an affected version.

What is CVE-2023-22066?

CVE-2023-22066 affects the InnoDB component of MySQL Server. Oracle lists the following versions as vulnerable:

MySQL 8.1.

The bug is easy to trigger by users with high-level (like root or superuser) privileges and network access. Crucially, there’s no need for user interaction: the attacker can trigger this remotely using MySQL's own network protocols.

CVSS 3.1 Base Score: 4.9
Severity: Medium (Availability Impact)
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H)

It does *not* allow data leakage or alteration – just service disruption.

Lead to denial of service for all database-backed applications

- Target via TCP/IP, local sockets, or other supported protocols

While the bug doesn't give the attacker access to data, bringing critical databases offline can cause massive headaches for businesses.

How Does the Exploit Work?

Oracle’s advisory (Original Vulnerability Note) is light on details, but community research and patch diffs indicate the flaw relates to mishandling specific SQL statements in InnoDB with invalid or malicious parameters. Triggering sequences with malformed transactions or certain DDL statements (like ALTER TABLE, DROP TABLE, or odd UPDATE queries) can cause the server to access memory improperly—resulting in a crash.

Example Exploit Scenario

Below is a lab-safe example of how a privileged user might trigger a crash exploiting the kind of logic flaw behind CVE-2023-22066:

Step 1: Login as Privileged User

mysql -u root -p

Step 2: Run Malicious Statement

Supposing the flaw is triggered by deleting from a crafted table in a certain way (*Note:* *Real-world PoC may differ as Oracle doesn’t disclose full details*).

CREATE TABLE doombug (id INT PRIMARY KEY) ENGINE=InnoDB;
-- Now we make InnoDB perform internal/malformed checks
ALTER TABLE doombug ADD COLUMN data BLOB NULL;
-- The following query pattern (hypothetically) triggers the bug
DELETE FROM doombug WHERE id = (SELECT id FROM doombug LIMIT 1 OFFSET 9999999);

After running such a query mix (depending on the exact bug), the server may hang or crash. You can observe the crash via logs (/var/log/mysql/error.log) or by MySQL becoming unresponsive.

> Warning: Do not test this on any production system! Even if the exact query above doesn’t crash your instance, variations on malformed SELECT/DELETE or complex DDL can do so in vulnerable versions.

The only safe mitigation is to update MySQL to a fixed version

- Patch: MySQL 8..35 or later
- Patch: MySQL 8.1.1 or later

References

- Oracle Advisory: Oracle MySQL July 2023 CPU
- NVD Entry: CVE-2023-22066
- MySQL Release Notes (8..35): Changes affecting security

Conclusion

CVE-2023-22066 highlights how even simple logic flaws in enterprise databases can knock over mission-critical infrastructure. The exploit is made serious by its low complexity and high repeatability—prone to exploitation by insiders with admin rights or lateral attackers.

If you manage MySQL servers, *patch as soon as possible*. Be wary of granting excessive privileges, and always monitor for odd queries from high-privilege accounts.

Timeline

Published on: 10/17/2023 22:15:12 UTC
Last modified on: 10/27/2023 15:15:10 UTC