CVE-2024-26210 - Inside Microsoft WDAC OLE DB Provider for SQL Server Remote Code Execution Vulnerability

In February 2024, Microsoft disclosed a significant security issue: CVE-2024-26210, a remote code execution (RCE) vulnerability in the Windows Defender Application Control (WDAC) OLE DB provider for SQL Server. While the description from Microsoft is brief, this vulnerability is crucial for system administrators, penetration testers, and anyone responsible for safeguarding Microsoft SQL Server environments. In this deep-dive, let’s break down what CVE-2024-26210 is, how it works, and what you can do to protect your infrastructure—using language anyone can understand.

What is CVE-2024-26210?

CVE-2024-26210 is a remote code execution weakness affecting the Microsoft OLE DB Provider for SQL Server in certain versions of Windows Defender Application Control (WDAC). Specifically, it lets attackers run arbitrary code on vulnerable Windows systems just by sending specially crafted requests. If an attacker tricks a user or server process into connecting to a malicious SQL database using the OLE DB provider, the attacker can take over the targeted machine.

Severity:

Technical Details

The vulnerability sits in the way the OLE DB provider processes certain network responses from SQL Server. If an attacker can control the database server you connect to—either directly or via an exposed connection string—they can inject data that corrupts memory and executes code of their choice.

#### Microsoft’s Summary (from February Patch Tuesday):

> A remote code execution vulnerability exists when the Microsoft OLE DB Provider for SQL Server improperly handles objects in memory. An attacker who successfully exploited this vulnerability could execute arbitrary code in the context of the local user.

How Exploitation Works (Example Flow)

1. Attacker Sets Up a Malicious SQL Server: Their server responds in a specific way during authentication or data exchange.
2. Victim Uses OLE DB Provider: This could happen directly (via sqlcmd, SSMS, or a custom application), or through phishing (malicious shortcut or file).
3. Exploit Triggered by Crafted Response: When the vulnerable client connects, the provider mishandles the attacker's response.
4. Code Execution: The attacker's payload runs with the same permissions as the user or application connecting.

Example Code Snippet

Let’s see a basic PowerShell snippet that might be used to connect to a SQL Server via OLE DB. This is not malicious, but it helps you understand where the vulnerability can be triggered—in real attacks, the attacker would make you connect to a malicious server:

# Example: PowerShell OLE DB Connection (harmless)
$connectionString = "Provider=SQLNCLI11;Server=SERVERNAME;Database=master;Integrated Security=SSPI;"
$connection = New-Object System.Data.OleDb.OleDbConnection($connectionString)
$command = $connection.CreateCommand()
$command.CommandText = "SELECT @@VERSION"
$connection.Open()
$version = $command.ExecuteScalar()
Write-Output $version
$connection.Close()

If SERVERNAME in that connection string pointed to a server under attacker control and your client was unpatched, a malicious payload could execute *before* the query even runs.

Proof-of-Concept Publicity

As of now, a full exploit has not been released publicly, but the flaw is trivial to trigger for those familiar with OLE DB internals. Security vendor Trend Micro Zero Day Initiative also classifies this as straightforward to exploit if you have access to the network the victim is on.

How to Protect Yourself

1. Apply Microsoft Patches ASAP:
Find the update info and approved hotfixes here:
https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2024-26210

2. Do Not Connect to Untrusted SQL Servers:
If a user or service connects to an attacker’s SQL server—via a phishing lure, a fake shortcut, or a web application—your system is at risk.

3. Audit ODBC/OLE DB Usage:
Check your environment for any scripts, legacy apps, or external components that use these providers (e.g. SQLNCLI, OleDbConnection, etc).

4. Network Segregation:
Restrict which servers your apps and services can connect to using firewalls, endpoint protection, or Windows Defender Application Control (WDAC) rules.

5. Monitor for Outbound SQL Connections:
Use EDR/SIEM tools to monitor unusual outbound connections to odd SQL servers.

Links & References

- Microsoft Security Guide: CVE-2024-26210
- Microsoft OLE DB Provider for SQL Server Docs
- Trend Micro ZDI: 2024 Patch Tuesday Analysis
- WDAC Overview

Conclusion

CVE-2024-26210 is a critical reminder that even foundational components like database providers can hide dangerous vulnerabilities for years. Patch now, audit your code for untrusted SQL connections, and use defense-in-depth to block possible attack chains! As more details and proof-of-concepts emerge, we’ll update this post with new information and recommendations.

Stay safe and keep those patches up to date. 🛡️


*This post is exclusive and written in easy-to-understand language for everyone—from IT admins to curious developers. For any updates, watch the Microsoft Security Response Center (MSRC) channel.*

Timeline

Published on: 04/09/2024 17:15:39 UTC
Last modified on: 04/10/2024 13:24:00 UTC