CVE-2024-48996: Microsoft SQL Server 2016 RCE Vulnerability

CVE-2024-48996 Overview

CVE-2024-48996 is a remote code execution vulnerability affecting the SQL Server Native Client component shipped with Microsoft SQL Server 2016, 2017, and 2019. The flaw is classified as a heap-based buffer overflow [CWE-122] and carries a CVSS 3.1 score of 8.8. Exploitation requires an authenticated user to connect to an attacker-controlled SQL Server, allowing the attacker to execute arbitrary code in the context of the connecting client process. Microsoft addressed the issue through its November 2024 security update cycle.

Critical Impact
An attacker who convinces a user to connect to a malicious SQL Server can execute code with the privileges of the client application, leading to full system compromise on affected hosts.

Affected Products

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

Discovery Timeline

2024-11-12 - Microsoft releases security update for CVE-2024-48996
2024-11-12 - CVE-2024-48996 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-48996

Vulnerability Analysis

The vulnerability resides in the SQL Server Native Client (SNAC), the client-side library used by applications to communicate with SQL Server instances via the Tabular Data Stream (TDS) protocol. The flaw is a heap-based buffer overflow [CWE-122] triggered when the client parses a specially crafted server response. A malicious SQL Server can return protocol data that exceeds the size expected by the client-side parser, corrupting heap memory adjacent to the target buffer.

Successful exploitation grants the attacker code execution in the context of the process hosting the SNAC library. Because SNAC is commonly loaded by database utilities, ETL tools, reporting services, and custom line-of-business applications, the impact extends well beyond database administrators. The EPSS score of 1.577% places this issue in the 72nd percentile for exploitation likelihood.

Root Cause

The root cause is insufficient bounds validation on length-prefixed fields returned by the SQL Server during connection negotiation and result set processing. The SNAC library allocates fixed or size-limited heap buffers based on assumed message structure but fails to validate that server-supplied length values fit within the allocated region before copying data.

Attack Vector

Exploitation is network-based but requires user interaction. An attacker must lure a victim into initiating an outbound SQL connection to a server the attacker controls. This is typically achieved through crafted .udl files, malicious ODBC data source configurations, phishing links that trigger connection strings, or compromised internal SQL endpoints. The attack complexity is low and no prior authentication to the malicious server is required.

The vulnerability mechanism is described in the Microsoft Security Update CVE-2024-48996 advisory. No public proof-of-concept exploit code has been released.

Detection Methods for CVE-2024-48996

Indicators of Compromise

Outbound TDS traffic (TCP/1433 or custom SQL ports) from workstations to untrusted or external IP addresses.
Unexpected child processes spawned by sqlcmd.exe, Management Studio (Ssms.exe), Excel.exe, or applications loading sqlncli11.dll.
Crash dumps or Windows Error Reporting entries referencing sqlncli11.dll or sqlncli.dll with heap corruption exceptions (0xC0000374).
Newly created ODBC or OLE DB data source entries pointing to unfamiliar servers.

Detection Strategies

Hunt for processes loading the SNAC DLLs and establishing outbound connections to non-corporate SQL endpoints.
Correlate DNS lookups and TDS connection attempts targeting recently registered or low-reputation domains.
Monitor for the loading of sqlncli*.dll by unusual parent processes such as Office applications or scripting hosts.

Monitoring Recommendations

Enable network egress logging for SQL protocols and alert on connections leaving trusted network segments.
Ingest Sysmon Event ID 7 (ImageLoad) and Event ID 3 (NetworkConnect) to link SNAC usage to network activity.
Track creation of .udl, .dsn, and connection-string files delivered via email or web downloads.

How to Mitigate CVE-2024-48996

Immediate Actions Required

Apply the November 2024 Microsoft security updates for SQL Server 2016, 2017, and 2019 across all systems where the Native Client is installed.
Inventory endpoints for the presence of sqlncli11.dll and msoledbsql.dll and confirm patched versions are deployed.
Restrict outbound TDS traffic (TCP/1433 and named-instance ports) at the perimeter firewall to approved SQL Server destinations only.
Educate users to avoid opening untrusted .udl, .dsn, or database connection files.

Patch Information

Microsoft released fixes as part of the November 2024 Patch Tuesday cycle. Refer to the Microsoft Security Update CVE-2024-48996 advisory for the specific cumulative update or GDR package matching each SQL Server version and build. The SQL Server Native Client is a deprecated component, and Microsoft recommends migrating client applications to the Microsoft OLE DB Driver for SQL Server (MSOLEDBSQL) or the ODBC Driver for SQL Server.

Workarounds

Block outbound connections from user workstations to external SQL Server ports where no business need exists.
Uninstall the legacy SQL Server Native Client on systems that do not require it and migrate applications to supported drivers.
Enforce application allow-listing to prevent unauthorized processes from loading SNAC libraries.

bash

# Verify SQL Server Native Client version on Windows hosts
Get-WmiObject -Class Win32_Product | Where-Object { $_.Name -like "*SQL Server*Native Client*" } | Select-Object Name, Version

# Block outbound TDS traffic to non-approved destinations (example)
New-NetFirewallRule -DisplayName "Block-Outbound-TDS" -Direction Outbound -Protocol TCP -RemotePort 1433 -Action Block