In February 2024, Microsoft patched a critical vulnerability tracked as CVE-2024-21370 affecting the WDAC OLE DB provider for SQL Server. This flaw allows attackers to remotely execute arbitrary code on the target system if exploited successfully. Let’s break down what this means, how the vulnerability works, and how attackers might exploit it—with a look at the details and some code to help you understand the problem.

What is WDAC OLE DB Provider for SQL Server?

Microsoft WDAC (Windows Data Access Components) OLE DB provider for SQL Server (MSOLEDBSQL) is a critical component that lets Windows applications communicate with SQL Server databases using OLE DB APIs. Many enterprise apps—old and new—still use this technology.

What is CVE-2024-21370?

CVE-2024-21370 describes a vulnerability in the way the WDAC OLE DB provider handles specially crafted requests or data. The vulnerability is classified as *Remote Code Execution* (RCE), meaning that a remote attacker who can send malicious data to the service can run code of their choice on the victim's machine. Depending on the context, this could lead to full system compromise.

- CVSS score: Usually considered HIGH to CRITICAL
- Attack vector: Network, remote, often with low complexity if the target application uses the provider insecurely
- Affected: Machines with vulnerable versions of MSOLEDBSQL, including SQL Server client apps and potentially web applications

How Does the Vulnerability Work?

The core of CVE-2024-21370 lies in improper handling of user-supplied input or network data by the WDAC OLE DB provider. In some cases, an attacker can cause the provider to process malicious OLE DB requests which result in memory corruption or unsafe code execution.

Typical Exploitation Scenario

1. Malicious SQL Statement: The attacker gets a vulnerable application (like a web app) to execute a specially crafted SQL request, sometimes by passing malicious input.
2. OLE DB Provider processes the request and mishandles the input, triggering a memory bug (like buffer overflow).
3. Arbitrary Code Execution: The flaw allows the attacker’s code to run with the privileges of the running application or service.

Example Exploit Scenario

Let’s imagine a simplified ASP.NET application that receives user input, passes it directly to a SQL database using OLE DB, and then renders the results.

Vulnerable C# Code Example

using System.Data.OleDb;

string connectionString = "Provider=MSOLEDBSQL;Data Source=servername;Initial Catalog=mydb;Integrated Security=SSPI;";
string userInput = Request.QueryString["user"]; // e.g., http://example.com/?user=admin

string query = "SELECT * FROM Users WHERE username = '" + userInput + "'";

using(OleDbConnection conn = new OleDbConnection(connectionString))
{
    conn.Open();
    OleDbCommand cmd = new OleDbCommand(query, conn);
    OleDbDataReader reader = cmd.ExecuteReader();
    // process results
}

A simple SQL injection? Maybe, but this is where CVE-2024-21370 can differ: Even without a classic injection, specially crafted input (including binary payloads or malformed queries) can trigger the vulnerability lower in the stack, in the provider itself.

Proof-of-Concept: Fuzzing for the Vulnerability

Microsoft did not publish a full exploit, but the advisory hints that certain malformed requests can cause the vulnerable MSOLEDBSQL provider to execute code. Here’s a testing script (pseudocode) you might use for fuzzing:

import pyodbc

# Use OLE DB provider
conn_str = (
    'Driver={OLE DB Driver 18 for SQL Server};'
    'Server=myserver;'
    'Database=mydb;'
    'Trusted_Connection=yes;'
)

payload = "'; DECLARE @a VARBINARY(MAX) = x[malicious_payload_here]; --"

try:
    cnxn = pyodbc.connect(conn_str)
    cursor = cnxn.cursor()
    cursor.execute("SELECT * FROM Users WHERE username = " + payload)
    for row in cursor:
        print(row)
except Exception as ex:
    print("Error:", ex)

This is NOT a weaponized exploit, but it demonstrates how malicious binary data (or complex OLE DB crafted arguments) might crash or commandeer the server.

Impact & Risks

If the application or service using the OLE DB provider runs as LocalSystem or an admin account, the attack can fully compromise the machine.

Common targets: Web applications, middle-tier servers, legacy client apps

- Network attacks: If exposed via the Internet or untrusted networks, attackers can exploit the vulnerability remotely
- Wormable: Some RCEs of this type have been used in automated malware/worms before

Mitigation & Patch

The solution is to update. Microsoft has released fixed versions in their February 2024 Patch Tuesday.

- Microsoft Security Update Guide – CVE-2024-21370
- NIST NVD Listing
- Microsoft OLE DB Driver for SQL Server Documentation

Update WDAC OLE DB provider (MSOLEDBSQL) to the latest patched version.

2. Avoid passing user input directly to SQL/OLE DB without strict filtering or parameterization.

Conclusion

CVE-2024-21370 is a high-impact vulnerability rooted deep in the Microsoft data access stack. If your organization runs web applications, server components, or any software that talks to SQL Server using the OLE DB provider, update immediately and review your application code for risky patterns.

Stay safe, stay updated.

Disclosure:
This post is a technical explanation for educational and remediation purposes only. No exploit code is provided or distributed—always patch vulnerabilities and use security best practices.

Timeline

Published on: 02/13/2024 18:15:54 UTC
Last modified on: 02/13/2024 18:22:53 UTC