A critical vulnerability, CVE-2023-21976, has been recently discovered in the MySQL Server product of Oracle MySQL, specifically in the Server: Optimizer component. Affected versions include 8..32 and prior, and the vulnerability can be easily exploited by a high privileged attacker who has network access via multiple protocols. Successful exploitation of this vulnerability can lead to unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of MySQL Server. This vulnerability has a CVSS 3.1 Base Score of 4.9, which signifies Availability impacts. The CVSS Vector is (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H).

Exploit Details

The vulnerability CVE-2023-21976 in MySQL Server can be exploited by high privileged attackers that have network access to the target system via multiple protocols. An attacker needs to inject specific queries or transactions that can cause MySQL Server to hang or repeatedly crash, resulting in a denial of service (DoS).

Code Snippet

To exploit this vulnerability, an attacker would need to execute a crafted SQL query or transaction. Here's an example code snippet that demonstrates this:

-- Attacker needs privileges to execute this query
-- Crafted malicious SQL query or transaction
    SELECT ...; # Insert malformed query or conditions

This specific code snippet is not intended to be used maliciously, but rather as an illustration of how an attack could potentially be carried out. More details on crafting a specific malicious SQL query or transaction can be found in the original references.

The following links provide more details about the vulnerability, as well as how it was discovered and the steps taken to address it:

1. Oracle Critical Patch Update Advisory: https://www.oracle.com/security-alerts/cpujul2022.html

2. CVE-2023-21976 - NVD Detail: https://nvd.nist.gov/vuln/detail/CVE-2023-21976

3. MySQL Server Security Updates: https://www.mysql.com/security/

Mitigation Recommendations

Organizations using the affected version of MySQL Server (8..32 and prior) should take immediate action to mitigate the impact of this vulnerability. It is highly recommended to:

1. Apply the necessary patches or update to a newer, unaffected version of MySQL Server. Always ensure you have a backup of your data before updating or applying patches.

2. Restrict access to MySQL Server by implementing a strong authentication and authorization policy, and only allowing trusted users to execute queries and transactions.

3. Monitor the logs for suspicious activities and query patterns that could indicate an attempted exploit. Have a contingency plan in place to address any successful attacks.

4. Regularly review and stay up-to-date with the latest security advisories from software vendors like Oracle.


CVE-2023-21976 is a critical vulnerability in the MySQL Server product of Oracle MySQL, affecting versions 8..32 and prior. It can be exploited by high privileged attackers to cause a hang or frequently repeatable crash (complete DOS) of MySQL Server. To protect your organization and its data from potential exploits, it is vital to apply the necessary patches, implement strong access policies, and stay informed about the latest security updates from software vendors.


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