In June 2023, Microsoft patched a serious security hole in their SQL Server OLE DB driver. Tracked as CVE-2023-36417, this vulnerability could let an attacker run their own code remotely through carefully crafted client-side interactions. If you’re running apps that connect via OLE DB, this affects you and your organization. But what actually went wrong? And how could it be exploited?

Let’s break down the issue, see a simplified code example, explore the real risk, and show where to get more details.

What is CVE-2023-36417?

CVE-2023-36417 is a Remote Code Execution (RCE) vulnerability in the Microsoft OLE DB Provider for SQL Server. The issue is caused by improper handling of memory when client applications use OLE DB to connect to SQL databases.

> In short: A maliciously crafted SQL response could make the vulnerable OLE DB provider run arbitrary code under the context of the client application.

Microsoft addressed this issue in their June 2023 security updates. It has a CVSS score of 7.8 (High), meaning it’s a serious issue that should not be ignored.

How Does This Vulnerability Work?

The root problem lies in how the OLE DB Provider parses data coming from the SQL Server. If an attacker can control or poison the SQL Server’s data—think an internal threat or a compromised server—they can send back data that triggers a bug in memory handling (like a buffer overflow).

When the OLE DB driver parses this malformed response, it could execute code injected in the payload, giving the attacker control over the client machine—not the SQL server itself, but the device or application connecting to it.

Let’s see a simple C# example of connecting with OLE DB

using System.Data.OleDb;

string connectionString = "Provider=MSOLEDBSQL;Data Source=compromised_sql_server;Integrated Security=SSPI;";
string query = "SELECT * FROM EvilTable"; // Assumed malicious payload

using (OleDbConnection connection = new OleDbConnection(connectionString))
{
    connection.Open();
    OleDbCommand command = new OleDbCommand(query, connection);
    OleDbDataReader reader = command.ExecuteReader();
    while (reader.Read())
    {
        // Vulnerable parsing of data if malicious payload is sent.
        Console.WriteLine(reader[]);
    }
}

If the server sends a response with a specially crafted binary column, the vulnerable OLE DB driver could misinterpret it, causing a memory corruption and code execution. Exploit code is not public, but red-teamers have shown a proof-of-concept is possible.

Exploit Scenario Explained

Picture a desktop app at a large company that uses OLE DB to connect to various internal SQL servers. An attacker climbs the network chain, compromises a low-security SQL Server, and sets up a payload in a binary column. When a user from finance runs their regular report, their OLE DB-based app pulls in the data—and the attacker’s code runs under the user’s privileges. This could be used for ransomware, lateral movement, or data exfiltration.

What Should I Do?

Patch immediately! Microsoft’s fixed OLE DB driver is available as of June 2023. Update your driver and redeploy applications if you statically link the provider.

Reference:
Microsoft Security Update Guide: CVE-2023-36417
MSOLEDBSQL download and update

Technical Breakdown: Why Was This Possible?

This bug was triggered during parsing of responses *before* input data was validated. Unsafe memory management in the OLE DB provider led to writing/reading out-of-bounds, which can be hijacked using classic buffer overflow tactics. The attacker’s code, delivered as part of the SQL server’s data, exploits these logic flaws.

Bottom Line

CVE-2023-36417 is a prime example of how legacy database connectivity code can become a liability for organizations large and small. If you use OLE DB in your .NET, classic ASP, or even old desktop apps, update your providers and audit your exposure.

Don’t let legacy protocols be the weakest link!
Questions about your exposure? Dig into the official docs and test your environments now.

References

- Microsoft Security Response Center – CVE-2023-36417
- Microsoft Data Access Components (MDAC) and OLE DB FAQ
- MSOLEDBSQL Release Notes
- Exploit-DB (no current public exploit)

Timeline

Published on: 10/10/2023 18:15:12 UTC
Last modified on: 11/02/2023 02:08:56 UTC