CVE-2023-22028 - Easy DoS Attack on Oracle MySQL Server’s Optimizer – Details, Exploit Example, and How to Stay Safe

In June 2023, Oracle published the details about a new vulnerability in its MySQL Server product—CVE-2023-22028. For database administrators and developers, this one’s a wake-up call. It targets one of MySQL’s core components—the Optimizer. In this post, I’ll walk you through what the bug is, how it can be exploited, and, most importantly, how you can secure your systems. If you rely on MySQL 5.7.43 or earlier, or 8..31 or earlier, read on.

What is CVE-2023-22028?

CVE-2023-22028 is a Denial of Service (DoS) vulnerability in MySQL Server’s Optimizer component. The Optimizer is what figures out the best way to execute SQL queries.

This flaw is “easily exploitable” (according to Oracle), and any high-privileged attacker with network access to your server (over typical protocols like MySQL TCP port 3306) could bring down your whole server by sending specially crafted queries. The result? Your MySQL Server hangs or crashes, and with repeated attacks, you’re left with a useless service.

CVSS v3.1 Score: 4.9 (on a 10-point scale)
Vector:

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

S:U - Unchanged scope

- C:N/I:N/A:H - No confidentiality/integrity impact, high availability impact

MySQL 8..31 and older

If you use any of these versions, your server is vulnerable to someone who has high-level access—for example, a disgruntled DBA or a compromised application account.

How Does It Work?

The bug lives in the Optimizer. If an attacker with high privileges fires off a SQL query crafted in just the right way—including some nested subqueries or joins (the exact payload is not publicly detailed, per Oracle’s usual policy)—the Optimizer gets confused, goes into a loop, or triggers a crash.

Proof-of-Concept (PoC) Code Snippet

Here’s a simplified pseudo-PoC (since full exploitation details are not published). It’s meant for educational and defensive purposes only! *Do not run this on any production system.*

Imagine you have a user account with SUPER or ALL privileges, and you connect using the mysql client:

-- Example query structure that could cause the DoS, based on open optimizer bugs in MySQL:

SELECT 
    (SELECT 
        COUNT(*) 
    FROM 
        information_schema.columns AS c1 
        JOIN information_schema.columns AS c2 
    ON c1.table_name = c2.table_name) 
FROM 
    information_schema.tables 
WHERE 
    EXISTS (
        SELECT 1 FROM information_schema.columns WHERE table_name = 'your_table'
    );

Disclaimer: This is a representative pattern—actual exploit queries may need to be far more complex and tailored to hit the exact optimizer bug. See the MySQL Bug Tracker and Oracle advisories for more info.

Users and applications can’t access the database—service goes down.

With repeated attack queries, your database may become permanently unavailable until you patch or severely restrict access.

Links to Original References

- Oracle CVE-2023-22028 Security Advisory
- NVD National Vulnerability Database Entry
- Oracle MySQL Release Notes
- MySQL Bug Database

Upgrade to MySQL 5.7.44+ or 8..32+ (or newer)

- Get packages from MySQL Downloads

2. Restrict Privilege Use

- Give SUPER/ALL privileges only to trusted users.

4. Monitor for Abnormal Queries

- Use tools like Percona Monitoring or native MySQL logs to track heavy/complex queries.

Summary

CVE-2023-22028 shows how even “internal-only” flaws can become a serious problem, especially as companies rely on complex data-driven applications and cloud-based architectures where user and privilege boundaries are blurry. This bug allows anyone with sufficient privilege and remote access to crash your database server over the network, causing outage and headaches.

Stay safe: PATCH, restrict access, and monitor those logs!

If you found this breakdown helpful, share it with your DBA and developer friends, and keep your eyes on the Oracle Security Patch Advisory for more updates.

Timeline

Published on: 10/17/2023 22:15:00 UTC
Last modified on: 10/19/2023 09:46:00 UTC