A significant vulnerability has been discovered in the MySQL Server product of Oracle MySQL (Component: Server: Connection Handling). Affected versions include 5.7.40 and prior, as well as 8..31 and prior. In this post, we'll provide a comprehensive understanding of the vulnerability, how to identify it, and steps to mitigate potential threats associated with it.

CVE-2023-21963: The Vulnerability at a Glance

The vulnerability, technically known as CVE-2023-21963, poses a genuine threat to organizations utilizing MySQL Server. It enables a high-privileged attacker with network access via multiple protocols to compromise the integrity and availability of MySQL Server. As a result, successful attacks can lead to unauthorized partial denial of service (Partial DoS) of the database server.

The vulnerability has a CVSS 3.1 Base Score of 2.7, making it relatively low-risk, but still potentially impactful. The CVSS Vector for this vulnerability is (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L).

Code Snippet and Exploit Details

Unfortunately, we cannot disclose specific exploit code or methods, as doing so may increase the vulnerability's impact. However, we can confirm that the vulnerability is found within the connection handling component of MySQL Server. This implies that an attacker could potentially disrupt the normal functioning of a MySQL Server instance by leveraging the vulnerability within this component and causing unauthorized service disruptions.

To better understand the issue, let's take a look at a general code snippet showcasing the MySQL Server connection handling process:

def handle_connection(conn, req):
    # Function to handle connections in MySQL Server
        # Connection and authentication code

        # Processing queries and handling transactions
        while not connection.closed:
            # Reading data from the connection

            # Implementing SQL commands or handling errors

    except Exception as e:
        # Log and handle the exception

        # Close the connection

The simplified code snippet above demonstrates the connection handling process in a typical MySQL Server. The vulnerability is likely located within this process, allowing an attacker to exploit the connection handling component by sending malicious requests, ultimately causing a partial DoS.

References and Mitigation

Oracle, the developer of MySQL Server, has acknowledged this vulnerability and has provided patches to address it. Patches for affected versions: Oracle Critical Patch Update Advisory - April 2023

Organizations using affected MySQL Server versions are strongly encouraged to apply the relevant patches promptly. Additionally, organizations should implement best practices for securing their database servers, such as using strong passwords, employing least privilege principles, and implementing network segmentation to restrict unauthorized access.


CVE-2023-21963 is a vulnerability within the MySQL Server product of Oracle MySQL, specifically in the connection handling component. Although the issue has a relatively low CVSS Base Score of 2.7, organizations using the affected versions should still address the problem and apply the recommended patches. Further, implementing and maintaining strong security practices is essential in protecting organizational assets and preventing cyber attacks.


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