CVE-2016-3949 in SIMATIC S7-300
Summary
by MITRE
Siemens SIMATIC S7-300 Profinet-enabled CPU devices with firmware before 3.2.12 and SIMATIC S7-300 Profinet-disabled CPU devices with firmware before 3.3.12 allow remote attackers to cause a denial of service (defect-mode transition) via crafted (1) ISO-TSAP or (2) Profibus packets.
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Analysis
by VulDB Data Team • 08/25/2022
The vulnerability CVE-2016-3949 affects Siemens SIMATIC S7-300 programmable logic controllers that operate in either Profinet-enabled or Profinet-disabled configurations. This issue represents a significant security flaw in industrial control systems where the affected devices can be remotely manipulated to trigger a denial of service condition, specifically causing a defect-mode transition that effectively renders the industrial process control system non-operational. The vulnerability impacts both Profinet-enabled devices running firmware versions prior to 3.2.12 and Profinet-disabled devices running firmware versions prior to 3.3.12, indicating a widespread exposure across Siemens industrial automation products.
The technical exploitation of this vulnerability occurs through the crafting of malicious ISO-TSAP or Profibus packets that are specifically designed to trigger the defect-mode transition in the affected PLC devices. ISO-TSAP (Transport Service Access Point) represents a layer in the OSI network model that handles transport layer communication, while Profibus is a fieldbus standard commonly used in industrial automation for communication between devices. Attackers can leverage these communication protocols to send malformed packets that cause the PLC to enter a defective operational state, effectively halting industrial processes that depend on these controllers. This represents a sophisticated attack vector that targets the fundamental communication mechanisms of industrial control systems, aligning with the CWE-119 weakness category for improper access to memory locations and the CWE-121 category for buffer overflow conditions that can lead to system instability.
The operational impact of CVE-2016-3949 extends far beyond simple service disruption, as these PLC devices are critical components in industrial process control systems that manage manufacturing processes, chemical plants, power generation facilities, and other critical infrastructure. When a defect-mode transition occurs, the PLC enters a state where it cannot properly execute its control functions, potentially leading to production halts, safety system failures, or even hazardous conditions in industrial environments. The remote nature of the attack means that adversaries can exploit this vulnerability from outside the industrial network perimeter, making it particularly dangerous for organizations that have limited network segmentation or inadequate security controls around their operational technology infrastructure. This vulnerability directly impacts the availability and integrity of industrial control systems, representing a significant threat to industrial cybersecurity and aligning with ATT&CK technique T1499.001 for Network Denial of Service.
Organizations should implement immediate mitigations including firmware updates to the latest versions that address the vulnerability, network segmentation to isolate industrial control systems from general enterprise networks, and enhanced monitoring of communication protocols to detect anomalous traffic patterns. The vulnerability demonstrates the importance of maintaining up-to-date industrial control system firmware and implementing proper network security controls in critical infrastructure environments. Additionally, organizations should conduct thorough vulnerability assessments of their industrial control systems and implement network access controls to prevent unauthorized access to critical industrial communication protocols. The remediation process should include comprehensive testing of updated firmware in non-production environments before deployment to ensure that the patches do not introduce operational issues in critical industrial processes. This vulnerability underscores the need for robust industrial cybersecurity practices that consider both the operational requirements of industrial processes and the security threats that can compromise industrial control systems.