CVE-2025-27540: Siemens Telecontrol Server Basic SQLi Flaw

CVE-2025-27540 Overview

A critical SQL injection vulnerability has been identified in Siemens TeleControl Server Basic that affects all versions prior to V3.1.2.2. The vulnerability exists in the internally used Authenticate method, which fails to properly sanitize user input before incorporating it into SQL queries. This flaw allows an unauthenticated remote attacker to bypass authorization controls, read from and write to the application's database, and execute arbitrary code with NT AUTHORITY\NetworkService permissions.

Critical Impact

Unauthenticated remote attackers can achieve complete database compromise and code execution with system-level privileges by exploiting the SQL injection vulnerability in the authentication mechanism.

Affected Products

• Siemens TeleControl Server Basic (All versions < V3.1.2.2)

Discovery Timeline

• April 16, 2025 - CVE-2025-27540 published to NVD
• August 19, 2025 - Last updated in NVD database

Technical Details for CVE-2025-27540

Vulnerability Analysis

This vulnerability is classified as CWE-89 (SQL Injection), one of the most dangerous web application security flaws. The affected application fails to properly sanitize input to the Authenticate method, allowing attackers to inject malicious SQL statements that are executed by the underlying database engine.

The vulnerability is particularly severe because it exists in the authentication mechanism itself, meaning no prior authentication is required to exploit it. Once an attacker successfully injects malicious SQL, they can bypass authentication entirely, extract sensitive data from the database, modify or delete records, and escalate to code execution with NT AUTHORITY\NetworkService permissions—a highly privileged Windows service account.

Root Cause

The root cause is improper input validation and sanitization in the Authenticate method used by TeleControl Server Basic. User-supplied input is directly concatenated or interpolated into SQL queries without using parameterized queries or prepared statements. This allows specially crafted input to break out of the intended query context and execute arbitrary SQL commands.

Attack Vector

The attack is network-based and requires the attacker to have access to port 8000 on a system running a vulnerable version of TeleControl Server Basic. The attacker sends malicious authentication requests containing SQL injection payloads to the exposed service endpoint. Since no authentication is required before exploiting the vulnerability, the attack surface is significant for any system with the vulnerable port accessible.

The exploitation path typically follows this sequence:

1. Attacker identifies a system with TeleControl Server Basic accessible on port 8000
2. Attacker crafts a malicious authentication request with SQL injection payload
3. The Authenticate method processes the payload without proper sanitization
4. Injected SQL executes with database privileges, potentially enabling data exfiltration or modification
5. Through SQL Server features like xp_cmdshell or other escalation techniques, the attacker may achieve code execution as NT AUTHORITY\NetworkService

Detection Methods for CVE-2025-27540

Indicators of Compromise

• Unexpected authentication attempts or failures on port 8000 with anomalous input patterns
• SQL error messages in application logs indicating syntax errors from malformed queries
• Database audit logs showing unusual query patterns, especially involving UNION, SELECT, or system stored procedures
• Evidence of NT AUTHORITY\NetworkService executing unexpected commands or processes

Detection Strategies

• Deploy network intrusion detection systems (IDS) with signatures for SQL injection patterns targeting port 8000
• Enable detailed logging on TeleControl Server Basic and monitor for authentication anomalies
• Implement database activity monitoring to detect unusual SQL query patterns or unauthorized data access
• Use endpoint detection and response (EDR) solutions to identify suspicious process execution under NetworkService context

Monitoring Recommendations

• Monitor network traffic to port 8000 for signs of SQL injection attempts, including common payloads like single quotes, UNION statements, and comment sequences
• Configure SIEM alerts for authentication failures accompanied by database errors
• Track any unexpected outbound connections from systems running TeleControl Server Basic
• Audit database access logs for queries originating from the application that access system tables or execute extended stored procedures

How to Mitigate CVE-2025-27540

Immediate Actions Required

• Upgrade Siemens TeleControl Server Basic to version V3.1.2.2 or later immediately
• If immediate patching is not possible, restrict network access to port 8000 using firewall rules to trusted IP addresses only
• Implement network segmentation to isolate systems running TeleControl Server Basic from untrusted networks
• Review database and system logs for any signs of prior exploitation

Patch Information

Siemens has released a security update addressing this vulnerability in TeleControl Server Basic version V3.1.2.2. Organizations should obtain the update through official Siemens channels and apply it as soon as possible. For detailed patch information and download links, refer to the Siemens Security Advisory SSA-443402.

Workarounds

• Block external access to port 8000 using perimeter firewalls and only allow connections from authorized internal systems
• Implement a Web Application Firewall (WAF) or application-layer gateway capable of inspecting and blocking SQL injection attempts
• Consider deploying the application behind a VPN to limit exposure to authenticated users only
• If the Authenticate feature is not required for your deployment, consult with Siemens support about disabling or restricting the affected functionality

# Example firewall rule to restrict access to port 8000 (Windows Firewall)
netsh advfirewall firewall add rule name="Block TeleControl External" dir=in action=block protocol=tcp localport=8000
netsh advfirewall firewall add rule name="Allow TeleControl Internal" dir=in action=allow protocol=tcp localport=8000 remoteip=192.168.1.0/24