CVE-2024-48994: Microsoft SQL Server 2016 RCE Vulnerability

CVE-2024-48994 Overview

CVE-2024-48994 is a remote code execution vulnerability in the Microsoft SQL Server Native Client. The flaw stems from a heap-based buffer overflow [CWE-122] in the client component used by applications to communicate with SQL Server instances. An attacker who convinces a user to connect to a malicious or compromised SQL Server can execute arbitrary code in the context of the connecting client. Microsoft rates the issue 8.8 on the CVSSv3.1 scale. The current EPSS probability is 3.005% (86.8 percentile), indicating elevated likelihood of exploitation activity relative to most CVEs.

Critical Impact

Successful exploitation allows remote code execution on hosts running vulnerable versions of Microsoft SQL Server 2016, 2017, and 2019 when a user is tricked into initiating a connection to an attacker-controlled server.

Affected Products

• Microsoft SQL Server 2016 (x64)
• Microsoft SQL Server 2017 (x64)
• Microsoft SQL Server 2019 (x64)

Discovery Timeline

• 2024-11-12 - CVE-2024-48994 published to NVD
• 2024-11-15 - Last updated in NVD database

Technical Details for CVE-2024-48994

Vulnerability Analysis

The vulnerability resides in the SQL Server Native Client (SNAC), the legacy data access component used by applications to communicate with SQL Server over Tabular Data Stream (TDS). Microsoft classifies the weakness under [CWE-122], a heap-based buffer overflow. Exploitation requires user interaction, indicating the attack path involves a client-initiated connection to a malicious endpoint rather than an unauthenticated server-side trigger. Successful exploitation grants the attacker the ability to execute code with the privileges of the process consuming the Native Client library. Because SNAC is embedded in numerous administrative tools, ETL pipelines, and legacy line-of-business applications, the attack surface extends well beyond the SQL Server engine itself.

Root Cause

The defect is a heap memory corruption condition triggered while the Native Client parses server-sent data structures. Insufficient validation of attacker-controlled length or type fields permits a write that exceeds the bounds of a heap allocation. The resulting corruption can be steered to achieve control of execution flow.

Attack Vector

The attack is network-based but requires user interaction. A typical scenario involves persuading a user to open a connection string, ODBC data source, or SSMS query targeting a server the attacker controls. The malicious server returns crafted TDS responses that trigger the heap overflow inside the client process. No authentication is required because the corruption occurs during connection negotiation. Refer to the Microsoft Security Update CVE-2024-48994 advisory for vendor-specific technical detail.

// No verified public proof-of-concept code is available for CVE-2024-48994.
// See the Microsoft Security Response Center advisory for technical details.

Detection Methods for CVE-2024-48994

Indicators of Compromise

• Unexpected outbound TCP/1433 or TCP/1434 connections from workstations, jump hosts, or developer endpoints to untrusted external IPs.
• Crashes or abnormal terminations of processes loading sqlncli11.dll or sqlncli10.dll, particularly with heap corruption exception codes such as 0xC0000374.
• Spawn of unexpected child processes (for example, cmd.exe, powershell.exe) from applications that load the SQL Server Native Client.

Detection Strategies

• Hunt for processes loading the Native Client DLLs that subsequently establish connections to non-corporate SQL Server hosts.
• Alert on WER (Windows Error Reporting) entries referencing heap corruption faults in modules that import sqlncli*.dll.
• Correlate outbound TDS traffic with newly created processes to identify suspicious connection chains initiated by office productivity or scripting hosts.

Monitoring Recommendations

• Inventory hosts where the SQL Server Native Client is installed, including third-party applications that bundle SNAC.
• Monitor egress firewall logs for SQL connections leaving the corporate network, which often indicate misuse or exploitation attempts.
• Track patch deployment status across SQL Server 2016, 2017, and 2019 instances using configuration management telemetry.

How to Mitigate CVE-2024-48994

Immediate Actions Required

• Apply the November 2024 Microsoft security updates for SQL Server 2016, 2017, and 2019 referenced in the MSRC advisory.
• Identify and patch standalone installations of the SQL Server Native Client distributed with applications, since updating the database engine alone may not replace the client library.
• Restrict outbound TDS traffic at the perimeter so internal clients cannot connect to arbitrary external SQL Server endpoints.

Patch Information

Microsoft has released fixes for all affected versions. Consult the Microsoft Security Update CVE-2024-48994 page for the cumulative update or GDR package that corresponds to each SQL Server build. Replace any redistributable copies of sqlncli.msi shipped with internal applications.

Workarounds

• Migrate applications from the deprecated SQL Server Native Client to the supported Microsoft OLE DB Driver for SQL Server (MSOLEDBSQL) or ODBC Driver for SQL Server.
• Block outbound connections on TCP/1433 and TCP/1434 from user workstations using host or network firewall rules until patches are deployed.
• Use application allowlisting to prevent untrusted connection strings or .udl files from being opened by end users.

# Example: block outbound SQL Server traffic from a Windows workstation
netsh advfirewall firewall add rule name="Block Outbound SQL TDS" \
    dir=out action=block protocol=TCP remoteport=1433,1434 \
    profile=any enable=yes