CVE-2024-35271: SQL Server 2016 RCE Vulnerability

CVE-2024-35271 Overview

CVE-2024-35271 is a remote code execution vulnerability in the Microsoft SQL Server Native Client Object Linking and Embedding Database (OLE DB) Provider. The flaw stems from a heap-based buffer overflow [CWE-122] in how the Native Client processes data returned from a SQL Server instance. An attacker who tricks an authenticated user into connecting a vulnerable client to an attacker-controlled SQL Server can execute arbitrary code in the context of the client process.

Critical Impact
Successful exploitation enables remote code execution on systems running SQL Server 2016, 2017, 2019, and 2022, leading to full compromise of confidentiality, integrity, and availability.

Affected Products

Microsoft SQL Server 2016
Microsoft SQL Server 2017
Microsoft SQL Server 2019
Microsoft SQL Server 2022

Discovery Timeline

2024-07-09 - CVE-2024-35271 published to NVD
2024-07-09 - Microsoft releases security patch via the Microsoft Security Update Guide
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-35271

Vulnerability Analysis

The vulnerability resides in the SQL Server Native Client OLE DB Provider, the client-side component used by applications to communicate with SQL Server instances. The provider mishandles structured response data sent from a SQL Server, leading to a heap-based buffer overflow on the client. The EPSS score is 1.854% at the 76.4 percentile, indicating elevated exploitation likelihood relative to most CVEs.

Exploitation requires user interaction. A user must initiate or accept a database connection to a malicious server, typically through a database client application, query tool, or linked-server configuration. Once the connection completes, the attacker returns crafted data that triggers the overflow in the client process memory.

Because the overflow occurs on the heap, attackers can corrupt adjacent allocations and ultimately redirect execution flow. Code runs with the privileges of the user invoking the OLE DB client, which often includes database administrators or service accounts holding broad access.

Root Cause

The root cause is improper length validation when parsing data structures returned by a remote SQL Server. Insufficient bounds checking during memory copy operations on the heap allows an oversized server response to overrun an allocated buffer [CWE-122].

Attack Vector

The attack vector is network-based with low complexity and no required privileges, but requires user interaction. An attacker hosts a malicious SQL Server endpoint and lures a victim into connecting using SQL Server Management Studio, a custom OLE DB-enabled application, or a linked server. Upon connection, the attacker delivers a crafted response that triggers the heap overflow and executes arbitrary code.

No verified public proof-of-concept code is available for this vulnerability. See the Microsoft Security Update Guide for vendor technical details.

Detection Methods for CVE-2024-35271

Indicators of Compromise

Unexpected outbound TCP connections from workstations or servers to untrusted hosts on port 1433 or other SQL Server ports.
Crashes or anomalous memory access violations in sqlncli11.dll, msoledbsql.dll, or related Native Client modules.
Spawning of cmd.exe, powershell.exe, or other LOLBins as child processes of database client applications such as ssms.exe or custom OLE DB consumers.
New persistence artifacts or scheduled tasks created shortly after a SQL client session to an external host.

Detection Strategies

Hunt for process trees where SQL client tools spawn shell interpreters or script engines.
Inspect endpoint telemetry for module loads of OLE DB Provider DLLs followed by suspicious memory allocation patterns.
Correlate firewall and proxy logs to flag database connections from internal clients to non-corporate IP ranges.

Monitoring Recommendations

Enable PowerShell and process command-line auditing on hosts running SQL Server administration tools.
Forward Sysmon Event ID 1 and Event ID 7 data for OLE DB modules into the SIEM for baseline analysis.
Alert on outbound SQL traffic crossing network egress boundaries from non-server endpoints.

How to Mitigate CVE-2024-35271

Immediate Actions Required

Apply the Microsoft security update for each affected SQL Server version listed in the Microsoft Security Update Guide.
Inventory all systems with SQL Server Native Client or msoledbsql installed and prioritize patching of administrative workstations.
Restrict outbound database protocol traffic at the perimeter to known internal SQL Server hosts.
Train database administrators to avoid connecting management tools to untrusted SQL Server endpoints.

Patch Information

Microsoft published patches for all supported SQL Server versions on 2024-07-09. Refer to the Microsoft Security Update Guide for build numbers and cumulative update identifiers corresponding to SQL Server 2016, 2017, 2019, and 2022.

Workarounds

Block outbound TCP 1433 and configured SQL listener ports from user workstations to external networks where the OLE DB client is not required.
Remove the SQL Server Native Client and Microsoft OLE DB Driver for SQL Server from endpoints that do not require local database connectivity.
Disable or restrict creation of linked servers that point to systems outside administrative control.

bash

# Example: block outbound SQL traffic on Windows hosts using Windows Firewall
New-NetFirewallRule -DisplayName "Block Outbound SQL 1433" -Direction Outbound -Protocol TCP -RemotePort 1433 -Action Block