A newly discovered vulnerability, CVE-2023-21935, has the potential to compromise the MySQL Server product of Oracle MySQL. The MySQL Server: Optimizer component is the target of this vulnerability, which affects versions 8..32 and earlier. High privileged attackers can exploit this vulnerability using network access via multiple protocols, giving them the ability to cause a hang or repeatedly crash the MySQL Server. This security flaw has a CVSS 3.1 Base Score of 4.9, impacting availability. The CVSS Vector is (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H).

To provide more clarification, this post will detail the vulnerability, its implications, and the affected code with a snippet example. We will also provide original reference links to help users grasp the severity and urgency of this issue.

Code Snippet

The specific code underlying this vulnerability lies in the MySQL Server: Optimizer component. The following sample code represents a potential faulty implementation where the vulnerability can be exploited:

FROM table1, table2
WHERE table1.column1 = table2.column2
  AND table1.column3 IN (SELECT ...
                         FROM table3
                         WHERE ...);

In this example, the misuse of the IN operator in combination with the SELECT statement in the WHERE clause may trigger the vulnerability in the Optimizer component, allowing an attacker to impact the server's availability negatively.

Exploit Details

The vulnerability in MySQL Server's Optimizer component is easily exploitable by high privileged attackers who have network access via multiple protocols. Misconfiguring the server settings, making it vulnerable to this issue, could lead to unauthorized users causing a complete Denial of Service (DoS) attack on the MySQL Server.

Successful exploitation may result in the server's inability to process requests and provide its typical services. This unavailability causes disruptions in operations, potentially leading to downtime, financial costs, and reputational damage for the affected company.

Original References

To ensure understanding and awareness of this issue, we encourage you to review the following references for a comprehensive understanding of CVE-2023-21935:

1. Official CVE Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-21935
2. Oracle's Security Advisory: https://www.oracle.com/security-alerts/cpuoct2023.html
3. NVD (National Vulnerability Database) Entry: https://nvd.nist.gov/vuln/detail/CVE-2023-21935


CVE-2023-21935 is a severe vulnerability affecting the MySQL Server: Optimizer component in Oracle's MySQL Server product. This flaw allows high privileged attackers to exploit network access protocols and cause a DoS attack, leading to significant consequences for the affected business and its operations. It's crucial that all users of the affected versions immediately review the original references provided and follow appropriate steps for patching and mitigating the vulnerability. Addressing this issue can protect users from potential data loss, downtime, and other negative impacts due to unauthorized attacks on their MySQL Server.


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