In this post, we will delve into CVE-2023-30987, a vulnerability in the IBM Db2 for Linux, UNIX, and Windows (includes Db2 Connect Server) versions 10.5, 11.1, and 11.5. This vulnerability allows an attacker to cause a denial of service (DoS) attack by executing a specially crafted query on certain databases. We will explore the details of the vulnerability, provide code snippets, and link to original references. Let's jump in!

Vulnerability Details

CVE-2023-30987 is a denial-of-service vulnerability that affects IBM Db2 for Linux, UNIX, and Windows. These versions include Db2 Connect Server versions 10.5, 11.1, and 11.5. According to IBM X-Force ID: 253440, attackers can exploit this vulnerability by submitting a carefully crafted SQL query to certain databases. This query exploits a flaw in the databases' handling of specific parameters, causing unresponsiveness or crash.

Exploiting CVE-2023-30987

To understand how an attacker might exploit this vulnerability, let's take a look at the following code snippet:

-- This SQL query is an example of how
-- an attacker might craft a malicious payload
-- to exploit the CVE-2023-30987 vulnerability
SELECT * FROM vulnerable_table
WHERE vulnerable_column = 1234
        SELECT * FROM another_vulnerable_table
        WHERE another_vulnerable_column = 'specially_crafted_string'

This fictional SQL query demonstrates how an attacker could exploit this vulnerability by targeting specific columns in vulnerable tables, comparing them to a crafted string in another vulnerable table. Successfully executing this query could result in a denial of service for the targeted databases by causing them to either become unresponsive or completely crash.

Mitigation and Patching

To mitigate and protect against the CVE-2023-30987 vulnerability, IBM recommends that affected users upgrade to the latest Db2 for Linux, UNIX, and Windows version (source). Users should apply patches provided by IBM as soon as possible. Additionally, users are encouraged to update their authentication mechanisms to prevent unauthorized access to their databases, minimizing the chances of an attacker submitting a malicious query to a vulnerable database.


CVE-2023-30987 is a critical vulnerability affecting IBM Db2 for Linux, UNIX, and Windows. By exploiting this vulnerability, an attacker could potentially cause denial-of-service attacks on specific databases. We have provided code snippets illustrating how an attacker might craft a malicious query to exploit this vulnerability, as well as mitigation steps to protect against it, including upgrading to the latest version of IBM Db2. Stay vigilant and ensure that your systems remain protected by updating regularly and following security best practices.


1. IBM X-Force ID: 253440 -
2. CVE-2023-30987 -
3. IBM Db2 Vulnerability -


Published on: 10/16/2023 21:15:10 UTC
Last modified on: 12/22/2023 21:07:56 UTC