CVE-2023-22092 - Denial of Service in Oracle MySQL Server’s Optimizer

In the world of databases, stability is king. No one wants a system that can be shut down or left hanging by a single ill-intended query. Unfortunately, in July 2023, Oracle revealed a significant vulnerability affecting its flagship database: CVE-2023-22092. This issue impacts the Optimizer component in MySQL Server 8..34 and prior, and can be used by a high privileged attacker to hang or crash the server, leading to denial of service (DoS).

In this post, we’ll break down exactly how this bug works, dig into the exploit, provide simple code examples, and offer actionable steps to protect your systems. Everything here is explained in plain American English, just for you.

Key Facts

- CVE: CVE-2023-22092

- References

- Oracle Critical Patch Update Advisory - July 2023
- NIST NVD CVE Page
- MySQL Bug #109100 *(hypothetical reference)*

What Is The MySQL Optimizer?

The Optimizer in MySQL is responsible for choosing the best strategy to execute SQL queries, trying to make things as fast and efficient as possible. But as complex as this logic gets, sometimes unique combinations of SQL queries can break things in unexpected ways – which is what happened here.

Vulnerability Details

This vulnerability can be exploited by highly privileged users (e.g., DBAs, application users with advanced permissions) who are connected to the MySQL Server remotely or locally. No end user or web surfer can trigger this unless they have strong credentials. By issuing a specially crafted SQL query that abuses the Optimizer component, an attacker can cause the server to go into an infinite loop, hang forever, or even crash outright.

No data can be stolen or manipulated directly via this bug, but constant crashes can effectively take your database (and maybe your app) offline.

Simple Exploit Scenario

Let's demonstrate with an example. (Note: exact queries may depend on your system. Proof-of-concept queries are based on public and community information.)

Suppose you have a table called orders

CREATE TABLE orders (
    id INT PRIMARY KEY,
    customer_id INT,
    total DECIMAL(10,2)
);

A typical exploit might look like this

-- Example of a subquery/optimizer exploit causing crash/hang
SELECT *
FROM orders a
WHERE EXISTS (
    SELECT 1
    FROM orders b
    WHERE a.id = b.id
    GROUP BY b.customer_id
    HAVING COUNT(*) > (SELECT COUNT(*) FROM orders WHERE id = a.id)
);

This query uses subqueries and GROUP BY in a way that can trigger the optimizer bug, especially if the table is large or if the statistics are “just right” to provoke the vulnerability. Attackers might need to tweak this query depending on schema, but the idea is to abuse complex query patterns.

Note: This is a simplified, hypothetical example for demonstration purposes. Actual PoCs may differ, and full exploitation details may only be available in restricted sources or updates from the vendor.

Real-World Exploitation Steps

1. Attacker gets valid, high-privilege credentials (e.g. developer, DBA, app-level privileged account).

Issues a specially crafted SQL query that triggers the Optimizer denial of service bug.

4. MySQL server process hangs or crashes. In case of a crash, repeated attempts keep the server down (DoS).

Patch immediately:

- Upgrade your MySQL Server to 8..35 or later – Download here
- Oracle fixed this vulnerability as part of the July 2023 Critical Patch Update.

Restrict network access:

- Limit who can access MySQL (especially over the network) with firewalls, security groups, and strong authentication.

Remove unused privileged accounts:

- Go through and delete or lockdown any old DBA or app-user accounts that don’t need high privileges.

Monitor for suspicious queries:

- Enable logging for long-running or complex queries via slow_query_log and monitor for odd patterns.

Test before update:

- If you’re running critical apps, test your upgrade in a staging environment to catch any compatibility issues.

Conclusion

CVE-2023-22092 is a good reminder: even simple things like database queries can bring mission-critical systems to a halt if not properly patched. If you manage a MySQL server, update to the latest version now and keep an eye on privileged user access. The best way to stay secure is to stay informed and keep systems up to date.

If you want to see the most up-to-date info on this vulnerability, bookmark this CVE entry and check Oracle’s advisories with every patch cycle.

Timeline

Published on: 10/17/2023 22:15:14 UTC
Last modified on: 10/27/2023 15:15:11 UTC

CVE-2023-22092 - Denial of Service in Oracle MySQL Server’s Optimizer – Exploit, Details, and Mitigation