CVE-2023-36728: MS ODBC Driver For SQL Server DOS Flaw

CVE-2023-36728 Overview

CVE-2023-36728 is a Denial of Service vulnerability affecting Microsoft SQL Server and its related connectivity drivers. This vulnerability allows a local attacker with low privileges to trigger a denial of service condition, disrupting database availability and potentially impacting dependent applications and services.

Critical Impact

Successful exploitation can cause service disruption to Microsoft SQL Server instances, affecting database availability and business-critical operations that depend on the database infrastructure.

Affected Products

• Microsoft SQL Server 2014 SP3, 2016 SP3, 2017, 2019, and 2022 (x64)
• Microsoft ODBC Driver for SQL Server (Windows, Linux, macOS)
• Microsoft OLE DB Driver for SQL Server

Discovery Timeline

• October 10, 2023 - CVE-2023-36728 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-36728

Vulnerability Analysis

This denial of service vulnerability exists within Microsoft SQL Server and its associated data connectivity components. The vulnerability is classified under CWE-125 (Out-of-Bounds Read), indicating that the issue stems from improper handling of memory operations during data processing.

The local attack vector requires an attacker to have local access to the target system with low-level privileges. No user interaction is required to exploit this vulnerability. While the vulnerability does not allow for data confidentiality or integrity compromise, it can significantly impact system availability by causing the affected SQL Server instance to become unresponsive or crash.

Root Cause

The vulnerability originates from an out-of-bounds read condition (CWE-125) in the way Microsoft SQL Server and its connectivity drivers handle certain operations. When specific conditions are met, the affected component attempts to read memory beyond the allocated buffer boundaries, leading to unexpected behavior that can result in service disruption.

Attack Vector

This vulnerability requires local access to the affected system. An authenticated attacker with low privileges can craft specific inputs or operations that trigger the out-of-bounds read condition in the SQL Server engine or connectivity drivers. The attack does not require any user interaction and can be executed directly against the vulnerable component.

The exploitation mechanism involves triggering memory access violations within the SQL Server process. When the out-of-bounds read occurs, it can cause the database engine to enter an unstable state, resulting in service termination or unresponsive behavior. This can cascade to affect all applications and services relying on the database.

Detection Methods for CVE-2023-36728

Indicators of Compromise

• Unexpected SQL Server service crashes or restarts without clear cause
• Windows Event Log entries indicating application errors in sqlservr.exe or related driver processes
• Memory access violation errors in SQL Server error logs
• Abnormal resource consumption patterns preceding service failures

Detection Strategies

• Monitor SQL Server error logs for memory-related exceptions and crash events
• Implement Windows Event Log monitoring for Application Error events associated with SQL Server processes
• Deploy endpoint detection solutions to identify unusual process behavior in database services
• Track SQL Server service availability metrics to detect service interruptions

Monitoring Recommendations

• Configure alerting for SQL Server service state changes and unexpected restarts
• Implement database connection monitoring to detect availability disruptions
• Enable verbose logging on SQL Server instances to capture detailed error information
• Monitor system memory utilization patterns for anomalies in SQL Server processes

How to Mitigate CVE-2023-36728

Immediate Actions Required

• Apply the latest security patches from Microsoft for SQL Server and related connectivity drivers
• Review and restrict local access to systems running SQL Server to minimize attack surface
• Implement monitoring for SQL Server service availability to quickly detect exploitation attempts
• Ensure database backup and recovery procedures are tested and ready for rapid restoration

Patch Information

Microsoft has released security updates to address this vulnerability. Organizations should apply the appropriate patches for their specific SQL Server versions and connectivity drivers. Detailed patch information is available in the Microsoft Security Advisory for CVE-2023-36728.

Affected versions include:

• Microsoft SQL Server 2014 SP3, 2016 SP3, 2017, 2019, and 2022
• Microsoft ODBC Driver for SQL Server (all platforms)
• Microsoft OLE DB Driver for SQL Server

Workarounds

• Restrict local system access to trusted users only pending patch deployment
• Implement network segmentation to limit access to database servers
• Enable SQL Server audit logging to track all database access and operations
• Consider implementing high-availability configurations to minimize service disruption impact

# Verify SQL Server version and patch level
sqlcmd -S localhost -Q "SELECT @@VERSION"

# Check current SQL Server service status
sc query MSSQLSERVER

# Review SQL Server error log for recent issues
sqlcmd -S localhost -Q "EXEC xp_readerrorlog 0, 1"