Oracle recently addressed a significant vulnerability—CVE-2024-21218—in its MySQL Server product. This flaw resides specifically in the InnoDB storage engine. Let’s break down what this means, how the vulnerability works, and what you can do to protect your systems.

What Is CVE-2024-21218?

CVE-2024-21218 is a security vulnerability that affects the MySQL Server product's InnoDB component. The following versions are impacted:

MySQL 9..1 and earlier

It allows a highly privileged attacker with network access to cause the MySQL server to crash or hang, leading to a Denial of Service (DoS). The attacker needs valid administrative access (like a DBA or higher), because the bug cannot be triggered by standard users.

> Severity: CVSS 3.1 Base Score – 4.9 (Availability Impact)
> Vector: AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H (Network exploitable, Low complexity, High privilege, No user interaction, High impact on availability)

What’s the Risk?

Attackers who have admin (or similar) privileges can abuse this vulnerability to crash or hang MySQL from anywhere over the network. The attack is repeatable—meaning a malicious admin or a compromised admin account could keep bringing down your database in just seconds.

Luckily, this bug does not allow attackers to steal or change data—but a total outage of your database server can still be devastating.

How Does the Exploit Work?

The vulnerability is triggered by maliciously crafted queries or operations that exploit a weakness in InnoDB's memory management or locking routines. Without getting too deep into the C source code, an attacker with sufficient privileges could, for example, create or manipulate certain InnoDB objects in rapid sequence, causing InnoDB to enter a disallowed or unstable state, leading to a server crash or hang.

Suppose an admin crafts a series of SQL commands to flood InnoDB’s internal management system

-- Example: Repeatedly create and drop tables to exhaust InnoDB resources
DELIMITER //

CREATE PROCEDURE innodb_crash()
BEGIN
  DECLARE i INT DEFAULT ;
  WHILE i < 10000 DO
    SET @stmt = CONCAT('CREATE TABLE test_table_', i, ' (id INT) ENGINE=InnoDB;');
    PREPARE s1 FROM @stmt;
    EXECUTE s1;
    DEALLOCATE PREPARE s1;

    SET @stmt = CONCAT('DROP TABLE test_table_', i, ';');
    PREPARE s2 FROM @stmt;
    EXECUTE s2;
    DEALLOCATE PREPARE s2;

    SET i = i + 1;
  END WHILE;
END //

DELIMITER ;

-- Now, call the procedure (requires admin rights)
CALL innodb_crash();

This type of operation, if executed repeatedly and in large volumes (possible only by an admin user), could trigger the bug in MySQL’s InnoDB engine, crashing the server or causing hangs.

Note: This code is illustrative. The actual attack vector may depend on the specific details of your setup and the version involved.

Anyone running unpatched MySQL 8..39, 8.4.2, or 9..1 (or earlier) is at risk.

- Most cloud/shared hosting providers have already applied Oracle's patches, but check with your provider or IT team to make sure.
- Only users with high privileges can exploit this flaw, making insider threats and compromised admin accounts the main risk.

How To Fix

1. Patch Immediately:
Oracle has released a patch in its April 2024 Critical Patch Update.

Download the latest MySQL server appropriate for your distribution:

MySQL Download Page

2. Limit Admin Access:
- Only grant administrative privileges (like CREATE, DROP, PROCESS, etc.) to users who absolutely require them.

Use strong passwords and two-factor authentication for all admin-level accounts.

3. Monitor MySQL Server Logs:
- Watch out for repeated table creation/dropping, or strange InnoDB errors and crashes.

- Example log entry to investigate

  [ERROR] InnoDB: Assertion failure in thread 12345
  [ERROR] mysqld: Got signal 11; ...

4. Regularly Audit User Accounts

References

- Oracle CVE-2024-21218 Security Advisory
- Oracle Critical Patch Update Advisory - April 2024
- MySQL Release Notes

Conclusion

While CVE-2024-21218 isn’t the most severe bug out there, it’s a big deal if your organization relies on MySQL and allows more than a handful of trusted admins. The main danger comes from inside your organization or a compromised admin account. Patch your systems and be vigilant about who has high-level database privileges.

Timeline

Published on: 10/15/2024 20:15:11 UTC
Last modified on: 10/16/2024 20:43:35 UTC