CVE-2026-67383: SQL Server Information Disclosure Flaw

CVE-2026-67383 Overview

CVE-2026-67383 is an information disclosure vulnerability in Microsoft SQL Server. The flaw allows an authenticated attacker to obtain sensitive data by triggering verbose error messages over a network connection. The issue is classified under [CWE-209]: Generation of Error Message Containing Sensitive Information.

An attacker with low-level database privileges can craft queries that cause SQL Server to return error output containing internal state, schema details, or other confidential information. The vulnerability requires network access to a targeted SQL Server instance and valid credentials, but no user interaction.

Critical Impact
Authenticated network attackers can extract sensitive server-side information through crafted queries that produce detailed error messages.

Affected Products

Microsoft SQL Server (specific supported versions per Microsoft advisory)
Deployments exposing SQL Server endpoints to authenticated users
Environments where low-privilege database accounts have query submission rights

Discovery Timeline

2026-09-08 - CVE-2026-67383 published to NVD
2026-09-08 - Last updated in NVD database

Technical Details for CVE-2026-67383

Vulnerability Analysis

The vulnerability originates in how SQL Server constructs error responses for certain failed operations. Instead of returning generic error text, the engine embeds contextual data drawn from server-side memory, query state, or metadata. An authenticated attacker submitting malformed or boundary-condition queries can coerce the server into disclosing this data.

Because the flaw requires only low privileges (PR:L) and no user interaction, any account with query submission rights becomes a potential source of leakage. Disclosed content may include schema fragments, internal identifiers, or fragments of data belonging to other sessions. The impact is confined to confidentiality; integrity and availability are unaffected.

The Exploit Prediction Scoring System (EPSS) rates the probability of exploitation at approximately 0.95%, placing it in the 59th percentile as of 2026-09-10.

Root Cause

The root cause is improper sanitization of error message content before transmission to the client [CWE-209]. Diagnostic paths intended for internal debugging surface sensitive fields in production responses. The absence of a normalization layer between error generation and client delivery allows internal state to escape trust boundaries.

Attack Vector

Exploitation occurs over the network against an authenticated SQL Server session. The attacker issues queries designed to fail in ways that produce detailed error output. By iterating query structures, the attacker enumerates information leaked across multiple error responses. See the Microsoft Security Update for CVE-2026-67383 for technical specifics.

Detection Methods for CVE-2026-67383

Indicators of Compromise

High volumes of failed queries from a single authenticated principal returning verbose error messages.
Repeated syntactically malformed queries targeting system catalogs, metadata views, or type conversion functions.
Client sessions capturing SQL Server error output at abnormally high rates.

Detection Strategies

Enable SQL Server audit specifications to log failed batch requests and error content for later review.
Correlate authentication events with query failure spikes to isolate probing behavior from legitimate workloads.
Baseline normal error rates per application account and alert on statistical deviations.

Monitoring Recommendations

Ingest SQL Server error logs and audit trails into a centralized analytics platform for cross-session correlation.
Monitor for unusual patterns of RAISERROR, type conversion failures, or arithmetic overflow errors originating from low-privilege accounts.
Track outbound response sizes on SQL endpoints to detect exfiltration through error-based extraction.

How to Mitigate CVE-2026-67383

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft Security Update for CVE-2026-67383 advisory.
Audit database principal privileges and revoke query rights from accounts that do not require them.
Restrict network exposure of SQL Server instances to trusted application tiers only.

Patch Information

Microsoft has published fix guidance through the Microsoft Security Response Center. Administrators should consult the Microsoft Security Update for CVE-2026-67383 for the applicable build numbers per SQL Server version and apply cumulative updates during the next available maintenance window.

Workarounds

Configure client applications to suppress verbose error propagation to end users and log errors server-side instead.
Enforce least-privilege database roles so that authenticated attackers have minimal query surface area.
Place SQL Server behind network segmentation and require jump-host access for administrative connections.

bash

# Configuration example
# Review Microsoft advisory for authoritative patch and hardening guidance
# https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-67383