In July 2023, Oracle released a critical security advisory for its MySQL server product, identifying a vulnerability tracked as CVE-2023-22064. This flaw affects the Server: Optimizer component and can have serious consequences for affected deployments—including the ability for a remote attacker to crash MySQL servers, taking them offline with a Denial of Service (DoS). In this post, we’ll break down what this means, walk through potential exploit details, and provide easy-to-follow guidance for securing your systems.

Read the official Oracle advisory here

CVSS score: 4.9 - Moderate (primarily impacts availability).

- Vector: (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H)
- Impact: High-privileged users can crash the MySQL service, resulting in a complete denial-of-service. No data leaks or escalated privileges, but a complete shutdown loophole.

MySQL servers at version 8..34 or older.

- Servers where high-privileged user accounts (like DBA, root, or powerful application accounts) are accessible over the network.

Technical Deep Dive

The flaw lies in how MySQL handles certain optimizer queries—the part of the server that decides how to execute SQL queries for best performance. Improper handling here can allow a user with high privileges and network access to submit crafted queries which trigger an edge case, crashing the service or making it hang.

Why is it “easily exploitable” for high-privileged attackers?

Because attackers need a login with substantial server permissions, but after that, the steps are trivial: they only need to run a crafted SQL statement via any allowed protocol.

Example Exploit

Here’s a simplified *demonstration* (sanitized to prevent misuse) of how a high-privileged attacker could crash a vulnerable MySQL server.

> Warning: All code snippets are for educational use—never attack networks you do not own!

1. Connect as a High-Privileged User

mysql -u root -p -h target-server

2. Run a Maliciously Crafted Query

Suppose (hypothetically, since Oracle does not disclose the exact trigger for security reasons) this bug is in the handling of a SELECT with a complex join/case/aggregation structure. The pattern may look like this:

-- WARNING: This is a generic simulation, not the real exploit
SELECT 
    CASE 
        WHEN (SELECT COUNT(*) FROM information_schema.tables WHERE table_schema LIKE '%') >  
        THEN (SELECT 1 UNION SELECT 2) 
        ELSE NULL 
    END 
FROM dual 
LEFT JOIN (SELECT * FROM information_schema.processlist WHERE command LIKE '%') t ON t.id = 1;

What happens?

If the underlying bug is triggered, the MySQL Optimizer enters a faulty state, leading to a server crash or repeated hanging. In production, repeated queries like this can take down the entire database cluster.

Exploit Details & Impact

- Attacker prerequisites: Must have high privileges (equivalent to root or admin-level MySQL user).

Effect: Crash or DoS of the MySQL server (the main mysqld process).

- No data theft: Attackers *cannot* read or change data directly. The threat is complete availability loss.

Guidance from Oracle

- Upgrade immediately to MySQL 8..35 or the latest version.

Sample log message

[ERROR] [MY-013183] [Server] Error during query execution: server crashed in optimizer phase

References

- Oracle Critical Patch Update Advisory - July 2023
- NVD Entry for CVE-2023-22064
- MySQL Release Notes

Conclusion

While CVE-2023-22064 only affects server *availability*, for production environments that rely on MySQL, this can be devastating. If you manage a MySQL 8. installation, check your version immediately, patch if you haven’t already, and secure your privileged accounts. Even though the bug requires high privileges, insider attacks and accidental misuse remain real risks.

> Stay safe—patch early, patch often!

Have questions or want more real-world security how-tos? Let us know and subscribe for more deep dives!


*This post is exclusive to this platform, made simple for everyone looking to keep their MySQL servers secure.*

Timeline

Published on: 10/17/2023 22:15:00 UTC
Last modified on: 10/19/2023 09:45:00 UTC