CVE-2026-67630 Overview
CVE-2026-67630 is an out-of-bounds read vulnerability in Microsoft SQL Server that enables an authenticated attacker to disclose sensitive information over a network. The flaw is categorized under [CWE-125] (Out-of-bounds Read) and allows a low-privileged attacker with network access to read memory contents beyond the intended buffer boundary. Successful exploitation results in confidentiality impact without affecting integrity or availability of the database server.
Critical Impact
An authenticated attacker with low privileges can trigger a memory read outside allocated buffers to disclose sensitive information from the SQL Server process over the network.
Affected Products
- Microsoft SQL Server (refer to the Microsoft Security Update Guide for specific affected versions)
Discovery Timeline
- 2026-09-08 - CVE-2026-67630 published to NVD
- 2026-09-08 - Last updated in NVD database
Technical Details for CVE-2026-67630
Vulnerability Analysis
CVE-2026-67630 is an out-of-bounds read condition in Microsoft SQL Server. The database engine reads data from a memory location outside the bounds of an allocated buffer during processing of attacker-influenced input. The disclosed memory can include database contents, session state, or other process memory adjacent to the target buffer.
The vulnerability requires network reachability to the SQL Server instance and valid authentication with low privileges. Exploitation does not require user interaction. The scope is unchanged, and only confidentiality is affected. The EPSS probability is 0.714%, placing the CVE in the 51st percentile for near-term exploitation likelihood.
Root Cause
The root cause is missing or incorrect boundary validation when SQL Server parses or processes structured input from an authenticated session. The engine dereferences memory past the end of a buffer, returning the contents to the requesting client. This class of defect is tracked as [CWE-125] and typically stems from off-by-one errors, incorrect length calculations, or trusting client-supplied size fields.
Attack Vector
An attacker authenticates to the SQL Server instance over the network using existing low-privileged credentials. The attacker then submits a crafted query, RPC call, or structured payload that triggers the vulnerable parsing routine. SQL Server returns memory contents beyond the intended buffer as part of the response. See the Microsoft Security Update Guide entry for authoritative technical details.
// No verified proof-of-concept code is available.
// Refer to the Microsoft Security Update Guide for technical details.
Detection Methods for CVE-2026-67630
Indicators of Compromise
- Anomalous query patterns from low-privileged database accounts, particularly those returning larger-than-expected result payloads.
- Unusual RPC or T-SQL calls invoking functions associated with structured input parsing shortly before large response sizes are observed.
- Repeated malformed queries from a single authenticated session that generate parser warnings or unexpected error messages in SQL Server logs.
Detection Strategies
- Audit SQL Server Extended Events and Error Logs for repeated exceptions or unusual memory access patterns during query execution.
- Correlate authentication events with subsequent high-volume data returns to identify accounts abusing minimal privileges.
- Deploy database activity monitoring (DAM) to flag deviations from established query baselines for each service account.
Monitoring Recommendations
- Enable SQL Server auditing for all logins and DML operations against sensitive databases and forward logs to a central SIEM.
- Monitor network traffic to TCP port 1433 (and configured alternates) for authenticated sessions from unexpected sources.
- Track patch compliance across SQL Server instances and alert on hosts running builds prior to the fix referenced in the Microsoft advisory.
How to Mitigate CVE-2026-67630
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft Security Update Guide to all affected SQL Server instances.
- Review and reduce the number of accounts with direct network access to SQL Server, enforcing least privilege for application logins.
- Rotate credentials for any low-privileged database accounts that could be leveraged by an authenticated attacker.
Patch Information
Microsoft has released a security update addressing CVE-2026-67630. Administrators should consult the Microsoft Security Update Guide to identify the correct cumulative update or GDR package for each SQL Server version and edition in their environment. Apply patches during the next maintenance window and validate database functionality after deployment.
Workarounds
- Restrict network access to SQL Server using firewall rules, network segmentation, and private endpoints so only trusted hosts can reach the database port.
- Enforce strong authentication and disable unused SQL logins to reduce the pool of accounts an attacker could compromise.
- Enable Transport Layer Security (TLS) for SQL Server connections to prevent credential theft that would enable this authenticated attack path.
# Example: restrict inbound access to SQL Server on Windows Firewall
New-NetFirewallRule -DisplayName "SQL Server - Restricted" \
-Direction Inbound -Protocol TCP -LocalPort 1433 \
-RemoteAddress 10.0.0.0/24 -Action Allow
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
