CVE-2026-54116: SQL Server Information Disclosure Flaw

CVE-2026-54116 Overview

CVE-2026-54116 is a type confusion vulnerability in Microsoft SQL Server that allows an authenticated attacker to disclose sensitive information over a network. The flaw is categorized under CWE-843, which covers access of a resource using an incompatible type. An attacker with low privileges on the database can send crafted queries that trigger improper type handling, causing SQL Server to return data the attacker should not be able to read.

Critical Impact
An authorized attacker with network access can extract confidential data from SQL Server instances by exploiting improper type handling during query processing.

Affected Products

Microsoft SQL Server (see Microsoft Vulnerability CVE-2026-54116 for specific build versions)

Discovery Timeline

2026-07-14 - CVE-2026-54116 published to NVD
2026-07-16 - Last updated in NVD database

Technical Details for CVE-2026-54116

Vulnerability Analysis

The vulnerability results from SQL Server accessing a resource using a type that does not match the actual object in memory. When the database engine processes certain crafted inputs, it interprets memory regions as a different data type than intended. This mismatch causes the engine to return raw bytes or structured data from adjacent memory to the querying session.

Because the confidentiality impact is rated high while integrity and availability remain unaffected, the flaw is purely an information disclosure primitive. The attacker cannot directly modify data or crash the service through this issue, but disclosed memory contents may include credentials, session tokens, or other database records used to escalate the attack.

Exploitation requires network reachability to the SQL Server endpoint and valid low-privileged credentials. No user interaction is required, and the attack complexity is low, meaning reliable exploitation does not depend on race conditions or environmental factors.

Root Cause

The root cause is improper type validation during resource access inside the SQL Server query processing path. The engine trusts type metadata associated with an object without verifying that the underlying memory matches the expected structure, a class of flaw defined by CWE-843.

Attack Vector

Exploitation occurs over the network using the Tabular Data Stream (TDS) protocol against an authenticated SQL Server session. A user with any authenticated database role can submit specially crafted statements or parameters that trigger the mismatched type access. The server then returns memory contents in query results, error messages, or side-channel responses.

The vulnerability is described in prose only. Microsoft has not published proof-of-concept code, and no public exploit is available. Refer to the Microsoft Security Response Center advisory for vendor-supplied technical details.

Detection Methods for CVE-2026-54116

Indicators of Compromise

Unusual query patterns from low-privileged accounts targeting system tables, metadata views, or type conversion functions.
Repeated SQL errors referencing type conversion or data corruption in SQL Server error logs.
Anomalous data volumes returned to authenticated sessions that historically issue small, scoped queries.

Detection Strategies

Enable SQL Server Audit to capture SELECT activity on sensitive schemas and correlate with authenticated principal names.
Deploy Extended Events sessions to log queries that trigger conversion errors or reference deprecated type coercion paths.
Baseline query behavior per service account and alert on statistical deviations in row counts, byte volumes, and error rates.

Monitoring Recommendations

Forward SQL Server audit logs and Windows event logs to a centralized analytics platform for correlation with authentication events.
Monitor logins from unexpected source IP addresses, especially for accounts intended only for application service use.
Track EPSS scoring updates for CVE-2026-54116, which currently sits near the 57th percentile, to detect increased exploitation probability.

How to Mitigate CVE-2026-54116

Immediate Actions Required

Apply the security update referenced in the Microsoft advisory for CVE-2026-54116 to all affected SQL Server instances.
Inventory all SQL Server deployments, including containerized and cloud-hosted instances, and prioritize internet-exposed or multi-tenant systems.
Review and revoke unnecessary database logins to reduce the population of accounts capable of exploiting the flaw.

Patch Information

Microsoft has published guidance and cumulative updates for affected SQL Server versions through the Microsoft Security Response Center. Administrators should consult the MSRC update guide entry for CVE-2026-54116 to identify the correct build for their edition and servicing baseline before deploying the patch to production.

Workarounds

Restrict network access to SQL Server TDS ports using firewall rules and network segmentation to limit the pool of potential attackers.
Enforce least privilege on database roles, ensuring application accounts cannot execute ad-hoc queries against sensitive schemas.
Enable SQL Server Audit and require multi-factor authentication on jump hosts used to access database servers.

bash

# Configuration example: restrict SQL Server access to known application subnets
New-NetFirewallRule -DisplayName "SQL Server TDS - App Tier Only" `
  -Direction Inbound `
  -Protocol TCP `
  -LocalPort 1433 `
  -RemoteAddress 10.20.30.0/24 `
  -Action Allow

# Deny all other inbound traffic to the SQL Server port
New-NetFirewallRule -DisplayName "SQL Server TDS - Deny Other" `
  -Direction Inbound `
  -Protocol TCP `
  -LocalPort 1433 `
  -Action Block