CVE-2026-67379: SQL Server RCE Vulnerability

CVE-2026-67379 Overview

CVE-2026-67379 is a stack-based buffer overflow vulnerability [CWE-121] in Microsoft SQL Server. The flaw allows an authorized attacker to execute arbitrary code over a network by triggering memory corruption on the server stack. Exploitation requires low privileges but high attack complexity, and impacts confidentiality, integrity, and availability across a changed security scope. Microsoft published the advisory on September 8, 2026, and the vulnerability is tracked in the Microsoft CVE-2026-67379 Update Guide.

Critical Impact
An authenticated attacker who successfully exploits CVE-2026-67379 can execute code in the context of the SQL Server process, potentially compromising the database host and adjacent systems.

Affected Products

Microsoft SQL Server (refer to the Microsoft Update Guide for supported version and build coverage)

Discovery Timeline

2026-09-08 - CVE-2026-67379 published to NVD
2026-09-09 - Last updated in NVD database

Technical Details for CVE-2026-67379

Vulnerability Analysis

The vulnerability is a stack-based buffer overflow inside SQL Server. An authenticated network attacker sends crafted input that exceeds the bounds of a fixed-size buffer on the stack. Writing past the buffer boundary corrupts adjacent stack memory, including saved return addresses or structured exception handlers. This corruption enables the attacker to redirect execution flow and run code within the SQL Server process.

The scope change indicates that a successful exploit affects resources beyond the vulnerable component itself. In SQL Server deployments, this often means a compromise reaches beyond the database engine into the host operating system context or linked services. High complexity reflects the specific conditions required to reliably shape the stack for code execution.

Root Cause

The root cause is improper bounds checking when SQL Server processes attacker-controlled input into a fixed-size stack buffer, consistent with the [CWE-121] classification. Microsoft has not published detailed root-cause information beyond the advisory summary.

Attack Vector

Exploitation occurs over the network against an authenticated SQL Server session. The attacker must hold valid credentials with at least low privileges on the database instance. No user interaction is required. Because the attack vector is network-based, any exposed SQL Server endpoint reachable by an authenticated adversary is in scope.

No verified public proof-of-concept code is available for CVE-2026-67379 at the time of publication. Refer to the Microsoft CVE-2026-67379 Update Guide for authoritative technical details.

Detection Methods for CVE-2026-67379

Indicators of Compromise

Unexpected crashes, access violations, or restarts of the sqlservr.exe process, particularly following anomalous authenticated queries.
Creation of child processes by SQL Server (for example cmd.exe, powershell.exe, or rundll32.exe) that are not part of normal database workloads.
Outbound network connections initiated from the SQL Server process to unfamiliar hosts.
Unusual authenticated logins from atypical source addresses immediately preceding service instability.

Detection Strategies

Monitor Windows Application and System event logs for SQL Server service faults and Watson error reports referencing stack corruption.
Enable SQL Server audit logging for successful and failed logins to correlate authenticated sessions with anomalous engine behavior.
Deploy endpoint detection tooling to flag process lineage anomalies where sqlservr.exe spawns interactive shells or script interpreters.

Monitoring Recommendations

Alert on SQL Server process crashes followed by service restarts within short time windows.
Baseline normal network egress from database hosts and alert on deviations.
Track privilege use and role membership changes on SQL Server principals to identify post-exploitation persistence.

How to Mitigate CVE-2026-67379

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft CVE-2026-67379 Update Guide to all affected SQL Server instances.
Inventory SQL Server deployments and prioritize internet-exposed or multi-tenant instances for patching.
Rotate credentials for accounts with database access following patch deployment.
Restrict network reachability of SQL Server endpoints to authorized clients only.

Patch Information

Microsoft has released updates addressing CVE-2026-67379. Consult the Microsoft CVE-2026-67379 Update Guide for the specific build numbers and cumulative updates that correspond to each supported SQL Server version.

Workarounds

Enforce least privilege on database accounts to reduce the pool of principals capable of triggering the vulnerable code path.
Segment SQL Server hosts behind firewalls and restrict TCP 1433 (and named-instance ports) to trusted application tiers.
Require strong authentication, including Windows Authentication or Microsoft Entra ID integration, and disable unused SQL logins.
Monitor for anomalous authenticated activity until patches are fully deployed.

bash

# Configuration example: restrict SQL Server access to trusted subnets using Windows Firewall
New-NetFirewallRule -DisplayName "SQL Server - Restrict 1433" \
  -Direction Inbound \
  -Protocol TCP \
  -LocalPort 1433 \
  -RemoteAddress 10.0.0.0/24 \
  -Action Allow