CVE-2025-40765: Siemens Telecontrol Server Disclosure Flaw

CVE-2025-40765 Overview

A critical information disclosure vulnerability has been identified in Siemens TeleControl Server Basic V3.1. The affected application exposes password hashes to unauthenticated remote attackers due to missing authentication for critical functions (CWE-306). This vulnerability allows attackers to obtain user credentials and subsequently authenticate to perform database operations, potentially compromising the entire industrial control system infrastructure.

Critical Impact

Unauthenticated remote attackers can obtain password hashes and gain full authenticated access to the database service, enabling complete compromise of industrial control system data and operations.

Affected Products

• Siemens TeleControl Server Basic V3.1 (All versions >= V3.1.2.2 < V3.1.2.3)

Discovery Timeline

• 2025-10-14 - CVE CVE-2025-40765 published to NVD
• 2025-10-21 - Last updated in NVD database

Technical Details for CVE-2025-40765

Vulnerability Analysis

This vulnerability stems from a missing authentication mechanism for critical functionality within the TeleControl Server Basic application. The affected component fails to properly restrict access to sensitive endpoints that expose user credential information, specifically password hashes. An unauthenticated attacker with network access to the vulnerable service can extract these hashes without any prior authentication or authorization.

Once password hashes are obtained, attackers can attempt offline cracking attacks or, depending on the hash algorithm and implementation, potentially use pass-the-hash techniques to authenticate directly to the database service. Successful exploitation grants the attacker the same privileges as legitimate users, enabling them to read, modify, or delete critical industrial control data.

Root Cause

The root cause of this vulnerability is classified as CWE-306: Missing Authentication for Critical Function. The TeleControl Server Basic application fails to enforce authentication checks on functionality that handles sensitive user credential data. This design flaw allows any network-accessible attacker to request and receive password hash information that should be protected behind authentication barriers.

Attack Vector

The attack vector is network-based and requires no authentication, user interaction, or special privileges. An attacker can remotely target the vulnerable TeleControl Server Basic installation over the network. The exploitation flow involves:

1. The attacker identifies a TeleControl Server Basic instance accessible over the network
2. Without authentication, the attacker sends requests to the vulnerable endpoint
3. The server responds with password hash information for database users
4. The attacker uses the obtained hashes for offline password cracking or direct authentication
5. With valid credentials, the attacker authenticates to the database service and performs privileged operations

This vulnerability requires no sophisticated attack techniques—the information disclosure occurs due to the complete absence of authentication controls rather than a bypass of existing protections.

Detection Methods for CVE-2025-40765

Indicators of Compromise

• Unexpected or anomalous unauthenticated network connections to the TeleControl Server Basic service ports
• Unusual database authentication attempts following periods of unauthenticated network activity
• Multiple failed login attempts followed by successful authentication from unknown IP addresses
• Evidence of credential harvesting or hash extraction in network traffic logs

Detection Strategies

• Monitor network traffic for unauthenticated requests to TeleControl Server Basic endpoints that return sensitive data
• Implement intrusion detection rules to identify patterns consistent with credential harvesting activity
• Audit database authentication logs for login attempts from IP addresses that previously made unauthenticated connections
• Deploy network segmentation monitoring to detect unauthorized access attempts to industrial control network segments

Monitoring Recommendations

• Enable comprehensive logging on all TeleControl Server Basic instances and forward logs to a centralized SIEM
• Configure alerts for any unauthenticated access attempts to sensitive service endpoints
• Monitor for unusual database query patterns that may indicate compromised credentials are in use
• Implement user behavior analytics to detect anomalous authenticated sessions following potential credential theft

How to Mitigate CVE-2025-40765

Immediate Actions Required

• Upgrade Siemens TeleControl Server Basic to version V3.1.2.3 or later immediately
• Restrict network access to TeleControl Server Basic installations using firewall rules and network segmentation
• Rotate all user passwords and database credentials as a precautionary measure
• Review authentication logs for signs of prior exploitation or unauthorized access
• Implement network monitoring to detect potential exploitation attempts while patching is in progress

Patch Information

Siemens has released version V3.1.2.3 of TeleControl Server Basic to address this vulnerability. Organizations should apply this update as soon as possible. For detailed patch information and download instructions, refer to the Siemens Security Advisory SSA-062309.

Workarounds

• Isolate TeleControl Server Basic systems on dedicated network segments with strict access controls
• Implement network-level authentication and access restrictions to limit exposure to trusted IP ranges only
• Deploy additional network monitoring and intrusion detection to identify exploitation attempts
• Consider disabling remote network access to the service entirely until patching can be completed, if operationally feasible

# Network segmentation example - restrict access to TeleControl Server
# Adjust IP ranges according to your environment
iptables -A INPUT -p tcp --dport 8080 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP