CVE-2024-26186: Microsoft SQL Server 2016 RCE Vulnerability

CVE-2024-26186 Overview

CVE-2024-26186 is a remote code execution vulnerability in the Microsoft SQL Server Native Scoring feature. The flaw is rooted in a use-after-free condition [CWE-416] within the database engine. An authenticated attacker with low privileges can send crafted queries that trigger the freed memory reuse, leading to arbitrary code execution in the SQL Server process context. The vulnerability affects Microsoft SQL Server 2016, 2017, 2019, and 2022, along with the SQL 2016 Azure Connect Feature Pack. Successful exploitation compromises confidentiality, integrity, and availability of the database instance.

Critical Impact
A low-privileged attacker with network access to a vulnerable SQL Server instance can execute code inside the database service and pivot to the underlying host.

Affected Products

Microsoft SQL Server 2016 (x64) and SQL 2016 Azure Connect Feature Pack
Microsoft SQL Server 2017 (x64) and SQL Server 2019 (x64)
Microsoft SQL Server 2022 (x64)

Discovery Timeline

2024-09-10 - CVE-2024-26186 published to NVD
2026-08-10 - Last updated in NVD database

Technical Details for CVE-2024-26186

Vulnerability Analysis

The vulnerability resides in the Native Scoring functionality of Microsoft SQL Server. Native Scoring uses the PREDICT T-SQL function to execute pre-trained machine learning models directly inside the database engine without invoking external runtimes. The scoring path processes serialized model blobs and input rowsets in native code. The defect is classified as a use-after-free [CWE-416], meaning the engine references a memory object after that object has already been released. An attacker who submits a crafted PREDICT call with a malformed model or input schema can trigger the dangling reference. Reuse of the freed allocation allows the attacker to influence virtual function pointers or object metadata that the engine dereferences during scoring. The result is code execution inside the sqlservr.exe process, which typically runs under a service account with broad access to database data files, linked servers, and, depending on configuration, the host operating system.

Root Cause

The root cause is improper lifetime management of an internal object used during native model evaluation. The engine releases the object along one code path while another code path retains a pointer and later dereferences it, producing the use-after-free.

Attack Vector

Exploitation requires network access to the SQL Server endpoint and a valid login with permission to execute the PREDICT function. No user interaction is required. The attacker submits crafted scoring input to trigger the freed allocation and control subsequent memory reuse. Refer to the Microsoft Security Update CVE-2024-26186 advisory for vendor technical details. No public proof-of-concept exploit is available at the time of writing.

Detection Methods for CVE-2024-26186

Indicators of Compromise

Unexpected crashes or access violation dumps of sqlservr.exe referencing the Native Scoring or PREDICT code paths in the SQL Server error log.
Anomalous PREDICT T-SQL statements originating from application accounts that do not normally execute machine learning queries.
Child processes spawned by sqlservr.exe such as cmd.exe, powershell.exe, or rundll32.exe, which are not expected during normal database operation.
Outbound network connections from the SQL Server host to unfamiliar destinations shortly after suspicious query activity.

Detection Strategies

Enable SQL Server extended events or audit specifications to capture executions of the PREDICT function and correlate with the invoking login and source IP.
Hunt for process ancestry where sqlservr.exe is the parent of scripting or living-off-the-land binaries.
Monitor Windows Error Reporting and application crash telemetry for repeated faults in SQL Server modules tied to native scoring.

Monitoring Recommendations

Alert on new or rarely used database logins issuing PREDICT or model-loading statements against production instances.
Baseline normal SQL Server memory and CPU behavior and raise alerts on sudden anomalies that correlate with scoring workloads.
Forward SQL Server audit logs and host EDR telemetry to a central platform for cross-source correlation of query activity and process execution.

How to Mitigate CVE-2024-26186

Immediate Actions Required

Apply the Microsoft security update for CVE-2024-26186 to all affected SQL Server 2016, 2017, 2019, and 2022 instances, including the SQL 2016 Azure Connect Feature Pack.
Inventory database logins and revoke EXECUTE permission on the PREDICT function for accounts that do not require native scoring.
Restrict network exposure of SQL Server endpoints so that only trusted application tiers can reach TCP 1433 and named-instance ports.
Run the SQL Server service under a least-privileged account to limit post-exploitation impact on the host.

Patch Information

Microsoft has released fixed builds for each affected SQL Server version. Consult the Microsoft Security Update CVE-2024-26186 advisory to identify the correct cumulative update or GDR package for your servicing branch and apply it during a maintenance window.

Workarounds

Disable or block use of the Native Scoring PREDICT function on instances that do not use in-database machine learning.
Enforce network segmentation and firewall rules that limit SQL Server access to authorized application hosts only.
Require strong authentication and rotate credentials for any account with PREDICT execution rights until patching is complete.

bash

# Example: revoke PREDICT execution from a role until patches are deployed
REVOKE EXECUTE ON FUNCTION::PREDICT FROM [AppRole];