CVE-2026-68776: SQL Server Information Disclosure Flaw

CVE-2026-68776 Overview

CVE-2026-68776 is an information disclosure vulnerability in Microsoft SQL Server. The flaw stems from the use of an uninitialized resource [CWE-908], allowing an authenticated attacker to read memory contents over a network. Microsoft published the advisory on September 8, 2026 through the Microsoft Security Response Center (MSRC).

The vulnerability requires low-privileged authenticated access and no user interaction. Successful exploitation exposes confidential data residing in server memory but does not affect integrity or availability. The Exploit Prediction Scoring System (EPSS) score is 0.552% with a percentile of 44.35 as of September 10, 2026.

Critical Impact
An authorized attacker with network access to a vulnerable SQL Server instance can read uninitialized memory contents, potentially exposing sensitive database data, credentials, or query fragments.

Affected Products

Microsoft SQL Server (see the Microsoft CVE-2026-68776 Update Guide for the complete affected version list)

Discovery Timeline

2026-09-08 - CVE-2026-68776 published to NVD
2026-09-08 - Microsoft publishes advisory in MSRC Update Guide
2026-09-08 - Last updated in NVD database

Technical Details for CVE-2026-68776

Vulnerability Analysis

The vulnerability resides in SQL Server's handling of memory resources that are used before being initialized. When SQL Server allocates a resource such as a buffer, structure, or memory region, the code path fails to zero or properly populate the allocation before returning its contents to a caller. An authenticated attacker who can issue queries or invoke server functionality over the network can trigger the code path and receive residual data from previous operations.

The leaked contents may contain fragments of prior query results, table data, authentication tokens, or internal server state. Because SQL Server processes multi-tenant workloads on shared memory pools, the disclosed data can cross security boundaries between database users or sessions.

Root Cause

The root cause is classified as CWE-908: Use of Uninitialized Resource. The affected code path returns a resource to a caller without first ensuring that all bytes have been overwritten with intended data. Uninitialized bytes carry values left by earlier allocations, which the attacker can observe through the response.

Attack Vector

The attack requires network access to the SQL Server endpoint and valid credentials with at least low privileges on the target instance. No user interaction is required. The attacker submits crafted requests that exercise the vulnerable code path and reads back the response containing uninitialized memory contents. Repeated invocations can be used to harvest additional memory fragments.

No public proof-of-concept is available at this time, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2026-68776

Indicators of Compromise

Anomalous SQL query patterns from authenticated principals that repeatedly invoke the same function or stored procedure with varying input to enumerate memory contents.
Elevated volumes of small, low-cost queries returning binary or unexpected result data to a single client.
Authentication events from service or application accounts issuing queries outside their normal workload profile.

Detection Strategies

Enable SQL Server Audit to log EXECUTE and SELECT events on functions and procedures exposed to lower-privileged principals.
Correlate SQL authentication logs with network flow data to identify sessions performing high query volumes with abnormal result sizes.
Deploy database activity monitoring (DAM) rules that alert on repeated calls to the same routine returning variable-length binary output.

Monitoring Recommendations

Forward SQL Server error logs, audit logs, and Extended Events sessions to a centralized analytics platform for correlation.
Baseline normal query patterns per application account and alert on statistical deviations in call frequency and result volume.
Monitor for principals with db_datareader or higher role membership executing unusual system or extended stored procedures.

How to Mitigate CVE-2026-68776

Immediate Actions Required

Apply the security update referenced in the Microsoft CVE-2026-68776 Update Guide to all affected SQL Server instances.
Inventory SQL Server deployments, including containerized and cloud-hosted instances, and prioritize internet-exposed and multi-tenant systems.
Review database principal permissions and revoke unnecessary EXECUTE and SELECT grants on non-essential objects.

Patch Information

Microsoft has released a security update through the MSRC Update Guide. Administrators should consult the Microsoft CVE-2026-68776 Update Guide for the specific KB articles, cumulative updates, and GDR packages that apply to each SQL Server version in their environment. Apply the update through Windows Update, WSUS, SCCM, or the Microsoft Update Catalog according to your standard patching process.

Workarounds

Restrict network access to SQL Server TCP endpoints using firewall rules that permit only trusted application servers and administrative hosts.
Apply the principle of least privilege by removing unused logins and reducing role membership on production databases.
Enforce network segmentation between SQL Server hosts and general-purpose user networks to reduce the population of principals that can reach the endpoint.

bash

# Example: restrict SQL Server access using Windows Firewall
New-NetFirewallRule -DisplayName "SQL Server - Allow App Tier Only" `
  -Direction Inbound -Protocol TCP -LocalPort 1433 `
  -RemoteAddress 10.20.30.0/24 -Action Allow

New-NetFirewallRule -DisplayName "SQL Server - Block All Others" `
  -Direction Inbound -Protocol TCP -LocalPort 1433 -Action Block