CVE-2024-21415: Microsoft SQL Server 2016 RCE Vulnerability

CVE-2024-21415 Overview

CVE-2024-21415 is a remote code execution vulnerability in the Microsoft SQL Server Native Client OLE DB Provider. The flaw stems from a heap-based buffer overflow [CWE-122] in the database client component. An attacker can execute arbitrary code in the context of the user who connects to a malicious database server.

Exploitation requires user interaction. The targeted user must initiate a connection to an attacker-controlled SQL Server instance using the vulnerable OLE DB provider. Successful exploitation impacts confidentiality, integrity, and availability.

Critical Impact
An attacker who tricks a user into connecting to a malicious SQL Server can execute arbitrary code on the client system, leading to full compromise of the affected host.

Affected Products

Microsoft SQL Server 2016 (x64)
Microsoft SQL Server 2017 (x64)
Microsoft SQL Server 2019 (x64)
Microsoft SQL Server 2022 (x64)

Discovery Timeline

2024-07-09 - CVE-2024-21415 published to NVD
2025-01-15 - Last updated in NVD database

Technical Details for CVE-2024-21415

Vulnerability Analysis

The vulnerability resides in the SQL Server Native Client OLE DB Provider, the client-side component used by applications to connect to SQL Server. The component fails to validate the size of data returned by a remote SQL Server before copying it into a heap buffer. An attacker who controls the server-side responses can craft replies that overflow the destination buffer.

Because the overflow occurs on the heap, attackers can corrupt adjacent heap metadata or function pointers to redirect execution. Successful exploitation yields code execution in the context of the connecting user. The vulnerability affects all supported SQL Server releases from 2016 through 2022 on x64 platforms.

The EPSS probability sits at 1.688 percent, indicating moderate predicted exploitation activity. No public proof-of-concept code or in-the-wild exploitation has been confirmed at the time of writing.

Root Cause

The root cause is improper bounds checking when the OLE DB provider parses tabular data stream (TDS) responses from a remote SQL Server. The provider trusts length fields supplied by the server and allocates heap memory based on a different value than what is later copied. The mismatch produces a classic heap-based buffer overflow [CWE-122].

Attack Vector

The attack vector is network-based but client-side. An attacker stands up a malicious SQL Server instance and induces a victim to connect using a vulnerable client application. Connection triggers can include phishing emails containing .udl files, Office documents with embedded data connections, or malicious links handled by registered SQL connection helpers.

Once the client initiates the TDS handshake, the malicious server returns crafted response packets that overflow the heap buffer in the OLE DB provider. The attacker then leverages the overflow to hijack execution within the client process.

No verified public exploit code is available. Refer to the Microsoft Security Update Guide for vendor technical details.

Detection Methods for CVE-2024-21415

Indicators of Compromise

Outbound TDS connections (TCP/1433 or custom SQL ports) from workstations to unknown or external IP addresses
Unexpected child processes spawned by applications hosting the OLE DB provider, such as excel.exe, msaccess.exe, or custom line-of-business binaries
Crash dumps referencing msoledbsql.dll or sqlncli11.dll with heap corruption signatures
Newly created .udl files in user profile or temporary directories opened from email or browser downloads

Detection Strategies

Inventory hosts running the SQL Server Native Client or msoledbsql provider and correlate with patch state from vulnerability scanners
Hunt for processes loading msoledbsql.dll that subsequently spawn shells (cmd.exe, powershell.exe) or perform network reconnaissance
Alert on TDS protocol connections to non-corporate destinations, particularly from endpoints that do not normally act as database clients

Monitoring Recommendations

Enable Microsoft Defender or equivalent EDR telemetry for module loads of msoledbsql.dll and sqlncli*.dll
Log Windows process creation events (Event ID 4688) with command-line auditing to detect anomalous child processes from Office or scripting hosts
Monitor firewall and proxy logs for outbound TCP/1433 traffic to external addresses and block at the perimeter where business need does not exist

How to Mitigate CVE-2024-21415

Immediate Actions Required

Apply the Microsoft security update for CVE-2024-21415 to all SQL Server 2016, 2017, 2019, and 2022 instances and to any client hosts with the Native Client OLE DB provider installed
Block outbound TCP/1433 and other SQL listener ports at the perimeter for endpoints that do not require external database connectivity
Restrict the ability of standard users to open .udl, .odc, and other data connection files received via email or web downloads
Audit installed versions of msoledbsql.dll and the legacy sqlncli provider across the estate using software inventory tooling

Patch Information

Microsoft released fixes through the standard SQL Server cumulative update channel. Refer to the Microsoft Security Update Guide for CVE-2024-21415 for the specific KB articles and build numbers per SQL Server major version. Apply the matching cumulative update or GDR package for each affected build.

Workarounds

Remove or uninstall the SQL Server Native Client from systems that no longer require it, as the legacy client is deprecated
Configure host-based firewall rules to allow outbound SQL traffic only to approved internal database servers
Enforce Attack Surface Reduction rules that block Office applications from creating child processes and from making outbound network connections

bash

# Example: block outbound TDS to non-corporate networks via Windows Firewall
New-NetFirewallRule -DisplayName "Block External SQL TDS" `
  -Direction Outbound -Protocol TCP -RemotePort 1433 `
  -RemoteAddress Internet -Action Block