CVE-2024-0056: Microsoft.Data.SqlClient Auth Bypass Flaw

CVE-2024-0056 Overview

CVE-2024-0056 is a security feature bypass vulnerability affecting Microsoft's SQL data providers, specifically Microsoft.Data.SqlClient and System.Data.SqlClient. This vulnerability enables attackers to intercept and potentially manipulate data transmitted between applications and SQL Server databases by bypassing encryption protections that are expected to secure these communications.

Critical Impact

This security feature bypass allows network-based attackers to compromise the confidentiality and integrity of SQL database communications, potentially exposing sensitive data or enabling data manipulation in transit.

Affected Products

• Microsoft.Data.SqlClient (multiple versions)
• System.Data.SqlClient
• Microsoft SQL Server 2022
• Microsoft Visual Studio 2022
• Microsoft .NET Framework (versions 2.0 SP2 through 4.8.1)
• Microsoft .NET (including version 8.0.0)
• Windows 10 (versions 1607, 1809, 21H2, 22H2)
• Windows 11 (versions 21H2, 22H2, 23H2)
• Windows Server 2008, 2012, 2016, 2019, 2022, 2022 23H2

Discovery Timeline

• January 9, 2024 - CVE-2024-0056 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2024-0056

Vulnerability Analysis

This vulnerability is classified under CWE-319 (Cleartext Transmission of Sensitive Information), indicating a fundamental issue with how encrypted communications are handled within the affected SQL data providers. The flaw allows an attacker positioned on the network path between a client application and SQL Server to bypass the security features designed to protect database communications.

The vulnerability affects the encryption negotiation or enforcement mechanism within the SQL client libraries. When applications connect to SQL Server databases using the affected providers, the security controls intended to ensure encrypted communication can be circumvented, leaving sensitive database queries, credentials, and result sets potentially exposed to interception.

Root Cause

The root cause stems from improper implementation of security features within the Microsoft.Data.SqlClient and System.Data.SqlClient libraries. The vulnerability allows the encryption protection mechanisms to be bypassed during client-server communication, potentially resulting in sensitive data being transmitted in cleartext or through weakened encryption channels that an attacker can intercept and read.

Attack Vector

The attack requires network access, positioning the attacker in a man-in-the-middle scenario between the application and the SQL Server database. While no user interaction is required, the attack has high complexity due to the network positioning requirements. A successful exploit does not require any privileges on the target system.

An attacker who successfully exploits this vulnerability could:

• Intercept database queries containing sensitive information
• Capture authentication credentials transmitted to SQL Server
• View query results including potentially confidential business data
• Modify data in transit between the application and database

This vulnerability does not directly enable code execution but the information disclosure and potential data manipulation capabilities represent significant security risks for any organization relying on these SQL data providers for sensitive database operations.

Detection Methods for CVE-2024-0056

Indicators of Compromise

• Unexpected unencrypted SQL traffic on network segments where TLS/SSL should be enforced
• Anomalous connection patterns between application servers and SQL databases
• Evidence of man-in-the-middle tools or traffic interception on network infrastructure
• Database connection logs showing connections without expected encryption attributes

Detection Strategies

• Monitor network traffic for SQL Server communications (typically port 1433) that lack proper TLS encryption
• Implement network intrusion detection rules to identify SQL traffic anomalies or downgrade attempts
• Review application logs for unexpected connection behavior or authentication failures
• Deploy SQL Server auditing to track connection encryption status

Monitoring Recommendations

• Enable SQL Server connection auditing to log encryption status for all incoming connections
• Configure network monitoring to alert on unencrypted database traffic in production environments
• Implement endpoint detection to identify applications using vulnerable SQL client library versions
• Review NuGet package dependencies across .NET applications to identify vulnerable Microsoft.Data.SqlClient or System.Data.SqlClient versions

How to Mitigate CVE-2024-0056

Immediate Actions Required

• Apply security updates from Microsoft for all affected products immediately
• Inventory all applications using Microsoft.Data.SqlClient and System.Data.SqlClient libraries
• Update NuGet packages to patched versions of the SQL client libraries
• Review and enforce SQL Server connection encryption requirements at the server level

Patch Information

Microsoft has released security updates to address this vulnerability. Detailed patch information and download links are available through the Microsoft Security Update Guide for CVE-2024-0056. Organizations should apply the appropriate updates for:

• Microsoft.Data.SqlClient NuGet package updates
• System.Data.SqlClient NuGet package updates
• .NET Framework cumulative updates
• .NET 8.0 updates
• SQL Server 2022 cumulative updates
• Visual Studio 2022 updates
• Windows operating system security updates

Workarounds

• Enforce encrypted connections at the SQL Server level using the Force Encryption option
• Require Encrypt=true and TrustServerCertificate=false in all application connection strings
• Implement network segmentation to isolate SQL Server traffic from potentially compromised network segments
• Use IPsec or VPN tunnels for database communications until patches can be applied

# SQL Server connection string configuration example
# Ensure these settings are enforced in application configuration
ConnectionString="Server=myserver;Database=mydb;Encrypt=true;TrustServerCertificate=false;Integrated Security=true;"

# Verify installed Microsoft.Data.SqlClient version
dotnet list package | grep -i sqlclient