CVE-2024-21428 - Inside SQL Server Native Client OLE DB Provider Remote Code Execution Vulnerability

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When databases are the core of your business, security vulnerabilities aren’t just quirks—they can be catastrophic. One such recent critical flaw is CVE-2024-21428, which targets the SQL Server Native Client OLE DB Provider, leaving remote code execution doors wide open. Let’s break down this vulnerability, how it can be exploited, and what can be done to stop attackers dead in their tracks.

What is CVE-2024-21428?

CVE-2024-21428 is a Remote Code Execution (RCE) vulnerability discovered in the Microsoft SQL Server Native Client (SNAC) OLE DB Provider. It allows malicious actors to execute arbitrary code on the affected system by leveraging how the provider processes specially crafted data.

Severity: Critical

Official Microsoft Advisory:
Microsoft Security Update Guide: CVE-2024-21428

How The Exploit Works (Simply Explained)

Imagine the SQL Server OLE DB Provider as a translator—taking requests from an application and talking directly to the database. When this provider receives a query, it should only process what it is told, safely. CVE-2024-21428 breaks this safety.

A crafty attacker creates a data payload or query object that, when interpreted by the provider, causes it to mishandle memory. This lets the attacker inject malicious commands, giving them control over the server with the same rights as the SQL Server process.

Attacker sends a malicious OLE DB input to SQL Server using a network connection.

2. Provider processes this input, but due to improper validation, overwrites memory or invokes a bad function pointer.
3. Attacker’s code executes remotely, allowing arbitrary commands (like creating user accounts, downloading malware, or exfiltrating data).

Example Exploit Scenario

> *For educational purposes only. Do NOT attempt this on unauthorized systems!*

Suppose the victim runs a legacy business app that connects to SQL Server via the OLE DB Provider. The attacker creates a custom script or tool that initiates a connection and sends malformed data.

Here’s a Python proof-of-concept for simulating the vulnerability.
*(This does not exploit the issue directly but shows how one may interact with the vulnerable provider.)*

import pyodbc

# Replace with actual target details
server = 'target_sql_server'
database = 'master'
username = 'attacker'
password = 'password'

# The malformed query string demonstrating how an attacker may trigger the bug.
# In real exploits, this would be a payload that abuses the OLE DB Provider's flaw.
malicious_query = "SELECT * FROM sys.objects WHERE name = 'my_table'; -- Special payload here"

try:
    conn_str = (
        f'DRIVER={{SQL Server Native Client 11.}};'
        f'SERVER={server};DATABASE={database};'
        f'UID={username};PWD={password};'
    )
    conn = pyodbc.connect(conn_str)
    cursor = conn.cursor()
    cursor.execute(malicious_query)
    for row in cursor:
        print(row)
except Exception as e:
    print(f"Error: {e}")

Note:
A real exploit would craft a lower-level payload targeting the memory flaw in sqlncli.dll. This PoC just sets the stage for how attackers connect and inject data.

Exploit Details

- Technical Root Cause: Mishandling of specially crafted input (such as malformed queries or connection strings) leading to memory corruption.

Pre-conditions for exploit

- The system must have a vulnerable version of SQL Server Native Client OLE DB Provider exposed to untrusted networks/applications.

Apply the official Microsoft update released in March 2024.

Microsoft Security Advisory & Download Links

References & Further Reading

- Microsoft Security Update Guide: CVE-2024-21428
- NIST NVD Entry for CVE-2024-21428
- SQL Server OLE DB Documentation (Microsoft)

Final Thoughts

CVE-2024-21428 is as serious as they come—remote code execution vulnerabilities are the bread and butter for cyber criminals. If you use SQL Server Native Client OLE DB Provider (especially on exposed servers), patch as soon as possible. Modern software environments are only as safe as their weakest component. Don’t let your database be that weak link.

Timeline

Published on: 07/09/2024 17:15:13 UTC
Last modified on: 10/08/2024 16:13:52 UTC