CVE-2011-4508 in SIMATIC HMI panel
Summary
by MITRE
The HMI web server in Siemens WinCC flexible 2004, 2005, 2007, and 2008 before SP3; WinCC V11 (aka TIA portal) before SP2 Update 1; the TP, OP, MP, Comfort Panels, and Mobile Panels SIMATIC HMI panels; WinCC V11 Runtime Advanced; and WinCC flexible Runtime generates predictable authentication tokens for cookies, which makes it easier for remote attackers to bypass authentication via a crafted cookie.
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Analysis
by VulDB Data Team • 11/29/2021
The vulnerability identified as CVE-2011-4508 represents a critical weakness in Siemens HMI (Human Machine Interface) systems that affects multiple versions of WinCC flexible and WinCC V11 products. This flaw specifically targets the authentication mechanism within the HMI web server component, creating a pathway for unauthorized access that significantly undermines the security posture of industrial control systems. The vulnerability stems from the predictable generation of authentication tokens, which violates fundamental security principles and exposes critical infrastructure to potential compromise.
The technical implementation of this vulnerability lies in the cryptographic weakness of the cookie token generation algorithm used by Siemens HMI web servers. When users authenticate to these systems, the server generates session cookies containing authentication tokens that should be unpredictable and cryptographically secure. However, the implementation uses a predictable algorithm that allows attackers to compute valid tokens without knowledge of the actual user credentials. This predictable token generation directly maps to CWE-330, which describes the use of weak entropy sources in cryptographic operations, and aligns with ATT&CK technique T1566 for credential access through the exploitation of weak authentication mechanisms.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it provides attackers with persistent access to critical industrial control systems. Remote attackers can leverage this weakness to bypass authentication entirely, potentially gaining control over production processes, modifying operational parameters, or accessing sensitive operational data. The affected products include a wide range of Siemens HMI panels and runtime environments, making this vulnerability particularly concerning for industrial facilities that rely on these systems for process control and monitoring. The vulnerability affects both legacy WinCC flexible versions and newer WinCC V11 implementations, indicating a long-standing issue that persisted across multiple product generations.
The exploitation of this vulnerability requires minimal technical skill, as attackers only need to craft specific cookie values that match the predictable token format. This low barrier to entry makes the vulnerability particularly dangerous in industrial environments where security may not be prioritized as aggressively as in traditional IT systems. The attack surface includes any network-accessible HMI web server that has not been patched, potentially affecting manufacturing plants, process control facilities, and other industrial environments where Siemens HMI systems are deployed. Organizations should consider implementing network segmentation and monitoring for unusual authentication patterns as part of their defense-in-depth strategy.
Mitigation strategies for this vulnerability require immediate patching of affected systems through Siemens security updates, particularly for WinCC flexible versions before SP3 and WinCC V11 before SP2 Update 1. Network administrators should implement additional security controls including firewall rules to restrict access to HMI web servers, disable unnecessary web server functionality, and deploy intrusion detection systems to monitor for suspicious cookie usage patterns. The vulnerability also highlights the importance of proper cryptographic implementation in industrial control systems and reinforces the need for regular security assessments of operational technology environments. Organizations should also consider implementing multi-factor authentication mechanisms and regular security audits to prevent similar vulnerabilities from being introduced in future system deployments.