CVE-2024-21308: Microsoft SQL Server 2016 RCE Vulnerability

CVE-2024-21308 Overview

CVE-2024-21308 is a remote code execution vulnerability in the Microsoft SQL Server Native Client OLE DB Provider. The flaw is rooted in a use-after-free condition [CWE-416] within the OLE DB component used by SQL Server clients to connect to database servers. An attacker who convinces a victim to connect to a malicious SQL Server instance can execute arbitrary code in the context of the connecting user. Microsoft published the advisory on July 9, 2024 and the issue affects SQL Server 2016, 2017, 2019, and 2022 on x64 platforms.

Critical Impact
Successful exploitation grants attackers arbitrary code execution on the client host, with high impact to confidentiality, integrity, and availability when a user connects to an attacker-controlled SQL Server.

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-2024-21308 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-21308

Vulnerability Analysis

The vulnerability is a use-after-free condition [CWE-416] in the SQL Server Native Client OLE DB Provider. OLE DB is the data access interface that SQL Server clients use to communicate with database engines. When the provider processes responses from a SQL Server, it frees an internal object but continues to reference the dangling pointer. An attacker who controls the server response can place crafted data at the freed allocation and steer execution to attacker-controlled code.

The attack requires user interaction. A victim must initiate or be coerced into initiating a connection to a malicious SQL Server endpoint, for example by opening a crafted ODBC data source, an Excel or Power BI connection string, or a maintenance script that points at an attacker-controlled host. No privileges on the target host are required beyond the privileges of the connecting user.

Root Cause

The root cause is improper lifetime management of an OLE DB Provider object after an error or specific server response path. The freed object is reused during subsequent processing, allowing an attacker who shapes the server-side traffic to control memory contents at the dangling pointer location.

Attack Vector

The attack vector is network-based with low complexity and requires user interaction. An attacker hosts a malicious SQL Server instance that returns crafted protocol responses. When a client running a vulnerable Native Client connects, the provider triggers the use-after-free and executes attacker-controlled code in the security context of the client process. There is no public proof of concept and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

For exploitation primitives and protocol-level detail, refer to the Microsoft CVE-2024-21308 Advisory.

Detection Methods for CVE-2024-21308

Indicators of Compromise

Outbound TDS (TCP/1433 or dynamic SQL Server ports) connections from end-user workstations to untrusted external IP addresses or unfamiliar internal hosts.
Unexpected child processes spawned by sqlservr.exe, Excel.exe, Power BI Desktop, Mscoree.dll-hosted apps, or other OLE DB consumers shortly after a database connection event.
New or modified ODBC and OLE DB connection entries in HKLM\SOFTWARE\ODBC\ODBC.INI or user-level equivalents pointing at attacker-controlled servers.
Crash dumps or Windows Error Reporting events for processes loading sqlncli11.dll, msoledbsql.dll, or related Native Client libraries.

Detection Strategies

Hunt for processes loading the SQL Server Native Client OLE DB Provider DLLs that subsequently spawn shell interpreters such as cmd.exe, powershell.exe, or rundll32.exe.
Correlate process creation telemetry with network connection telemetry to flag client-initiated SQL connections to unapproved destinations.
Use behavioral identification rules to detect heap corruption patterns and anomalous control-flow inside Office, BI, and ETL tooling that consumes OLE DB.

Monitoring Recommendations

Enable Windows Event Tracing (ETW) and Sysmon module-load and network-connect events for hosts that use Native Client connectivity.
Forward endpoint and network telemetry to a central SIEM or data lake and build alerts for SQL client traffic leaving administrative network zones.
Track patch status of SQL Server Native Client and Microsoft OLE DB Driver for SQL Server across endpoints and servers as part of vulnerability management reporting.

How to Mitigate CVE-2024-21308

Immediate Actions Required

Apply the Microsoft security updates referenced in the Microsoft CVE-2024-21308 Advisory for all installed SQL Server 2016, 2017, 2019, and 2022 instances.
Inventory hosts that have the SQL Server Native Client (sqlncli) or Microsoft OLE DB Driver installed, including non-server endpoints used by analysts and developers.
Restrict outbound TDS traffic from user workstations so that only approved internal SQL Server endpoints are reachable on TCP/1433 and the SQL Browser UDP/1434.

Patch Information

Microsoft addressed CVE-2024-21308 through cumulative updates for SQL Server 2016, 2017, 2019, and 2022. The fix corrects the object lifetime handling in the Native Client OLE DB Provider. Refer to the Microsoft CVE-2024-21308 Advisory for the exact build numbers and KB references applicable to each supported branch.

Workarounds

Block outbound connections to untrusted SQL Server endpoints at the host firewall and network egress points.
Discourage and detect ad-hoc connection strings in Office and BI tools that point at external or unmanaged servers.
Where feasible, migrate applications from the legacy SQL Server Native Client to the supported Microsoft OLE DB Driver for SQL Server (MSOLEDBSQL) at a patched version.

bash

# Example: restrict outbound TDS traffic on a Windows endpoint to approved SQL hosts
New-NetFirewallRule -DisplayName "Block-Outbound-TDS-Untrusted" `
  -Direction Outbound -Protocol TCP -RemotePort 1433 `
  -Action Block -Profile Any

New-NetFirewallRule -DisplayName "Allow-Outbound-TDS-Approved" `
  -Direction Outbound -Protocol TCP -RemotePort 1433 `
  -RemoteAddress 10.10.20.0/24,10.10.21.15 `
  -Action Allow -Profile Any