CVE-2025-49759: SQL Server 2016 Privilege Escalation Flaw

CVE-2025-49759 Overview

CVE-2025-49759 is a SQL injection vulnerability affecting multiple versions of Microsoft SQL Server. The flaw stems from improper neutralization of special elements used in SQL commands [CWE-89]. An authenticated attacker can leverage this weakness to elevate privileges over a network.

Microsoft published the advisory on August 12, 2025. The vulnerability impacts SQL Server 2016, 2017, 2019, and 2022. Successful exploitation grants the attacker elevated privileges with high impact on confidentiality, integrity, and availability of the database instance.

Critical Impact
An authenticated network attacker can inject crafted SQL statements to escalate privileges within Microsoft SQL Server instances, leading to full compromise of the database engine.

Affected Products

Microsoft SQL Server 2016 (x64)
Microsoft SQL Server 2017 (x64)
Microsoft SQL Server 2019 (x64)
Microsoft SQL Server 2022 (x64)

Discovery Timeline

2025-08-12 - CVE-2025-49759 published to NVD
2025-08-12 - Microsoft releases security advisory for CVE-2025-49759
2025-08-14 - Last updated in NVD database

Technical Details for CVE-2025-49759

Vulnerability Analysis

The vulnerability is classified under [CWE-89], Improper Neutralization of Special Elements used in an SQL Command. SQL Server fails to properly sanitize attacker-controlled input passed to internal SQL command processing. The flaw allows an authenticated user to inject crafted SQL syntax that executes in a higher-privileged context.

The attack requires valid credentials but no user interaction. An attacker with low-privileged database access can submit malformed input through an affected query path. The injected SQL is then executed with privileges beyond those assigned to the calling principal.

The Exploit Prediction Scoring System (EPSS) places this issue at the 78th percentile, indicating elevated probability of exploitation attempts compared to typical CVEs. Microsoft has not reported observed exploitation in the wild, and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog.

Root Cause

The root cause is missing or inadequate input sanitization within a SQL command handler in the database engine. Special SQL metacharacters submitted by an authenticated principal are not neutralized before being concatenated into a privileged query. This permits the attacker to alter SQL semantics and execute statements outside their assigned authorization scope.

Attack Vector

The attack vector is network-based against the SQL Server endpoint, typically TCP port 1433 or named instances. An attacker authenticates with valid SQL Server credentials or Windows credentials mapped to a login. The attacker then submits a crafted payload through an application interface or direct database connection that reaches the vulnerable code path. Successful exploitation yields privilege escalation within the SQL Server instance, enabling read or modification of data, configuration changes, and execution of administrative operations.

No public proof-of-concept code has been released for this vulnerability. Refer to the Microsoft CVE-2025-49759 Advisory for technical details and patch information.

Detection Methods for CVE-2025-49759

Indicators of Compromise

Unexpected execution of high-privilege stored procedures or DDL operations by low-privileged logins.
SQL statements in audit logs containing unusual concatenations of quotes, comments (--, /* */), or stacked queries from application accounts.
New logins, role memberships, or permission grants that do not match change-management records.
Anomalous query patterns originating from application service accounts outside normal business hours.

Detection Strategies

Enable SQL Server Audit and capture SCHEMA_OBJECT_ACCESS_GROUP, DATABASE_PERMISSION_CHANGE_GROUP, and SERVER_ROLE_MEMBER_CHANGE_GROUP events.
Deploy Extended Events sessions targeting sql_statement_completed and error_reported to surface malformed or injection-style queries.
Correlate application-tier web logs with database query telemetry to identify injection attempts that reach the database engine.
Baseline normal query profiles per login and alert on deviations such as unexpected use of xp_cmdshell, OPENROWSET, or EXECUTE AS.

Monitoring Recommendations

Forward SQL Server audit and Extended Events output to a centralized SIEM for long-term retention and correlation.
Monitor for privilege changes on sysadmin, db_owner, and securityadmin roles in near real time.
Track patch state across all SQL Server instances and alert when unpatched instances accept network connections.

How to Mitigate CVE-2025-49759

Immediate Actions Required

Apply the Microsoft security update for CVE-2025-49759 to all SQL Server 2016, 2017, 2019, and 2022 instances.
Inventory all SQL Server deployments, including containerized and cloud-hosted instances, and prioritize internet-exposed systems.
Rotate credentials for any SQL Server login that may have been used by an attacker and review recent privilege changes.
Restrict network exposure of SQL Server endpoints to trusted application tiers using firewall rules and network segmentation.

Patch Information

Microsoft has released security updates addressing CVE-2025-49759. Administrators should consult the Microsoft CVE-2025-49759 Advisory for the cumulative update or GDR package matching each SQL Server build. Apply updates through Microsoft Update, WSUS, or by downloading the build-specific installer from the Microsoft Update Catalog.

Workarounds

Enforce least-privilege login design so application accounts cannot reach administrative procedures or cross-database resources.
Use parameterized queries and stored procedures in application code to limit the injection surface presented to the database engine.
Disable unused features such as xp_cmdshell, CLR integration, and OPENROWSET ad hoc queries where not required.
Restrict SQL Server TCP listeners to internal management networks and require TLS for all client connections.

bash

# Configuration example - audit privileged actions and reduce attack surface
sqlcmd -S <instance> -Q "
CREATE SERVER AUDIT SqlInjectionAudit TO FILE (FILEPATH = 'C:\SQLAudit\');
ALTER SERVER AUDIT SqlInjectionAudit WITH (STATE = ON);

CREATE SERVER AUDIT SPECIFICATION SqlInjectionAuditSpec
FOR SERVER AUDIT SqlInjectionAudit
  ADD (SERVER_ROLE_MEMBER_CHANGE_GROUP),
  ADD (DATABASE_PERMISSION_CHANGE_GROUP),
  ADD (SCHEMA_OBJECT_ACCESS_GROUP)
WITH (STATE = ON);

EXEC sp_configure 'show advanced options', 1; RECONFIGURE;
EXEC sp_configure 'xp_cmdshell', 0; RECONFIGURE;
EXEC sp_configure 'Ad Hoc Distributed Queries', 0; RECONFIGURE;
"