CVE-2018-4850 in SIMATIC S7-400
Summary
by MITRE
A vulnerability has been identified in SIMATIC S7-400 (incl. F) CPU hardware version 4.0 and below (All versions), SIMATIC S7-400 (incl. F) CPU hardware version 5.0 (All firmware versions < V5.2), SIMATIC S7-400H CPU hardware version 4.5 and below (All versions). The affected CPUs improperly validate S7 communication packets which could cause a Denial-of-Service condition of the CPU. The CPU will remain in DEFECT mode until manual restart.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 03/13/2023
The vulnerability identified as CVE-2018-4850 affects Siemens SIMATIC S7-400 series programmable logic controllers including the S7-400H models with specific hardware and firmware versions. This issue represents a critical weakness in industrial control systems that could severely impact operational continuity and safety. The affected hardware spans multiple generations including CPUs with hardware version 4.0 and below, hardware version 5.0 with firmware versions prior to V5.2, and S7-400H CPUs with hardware version 4.5 and below. These controllers are widely deployed in critical infrastructure sectors including manufacturing, process control, and energy management systems where reliability is paramount.
The technical flaw stems from improper validation of S7 communication packets within the affected CPU implementations. S7 communication protocol is fundamental to Siemens industrial automation systems, enabling communication between programmable logic controllers and various devices including HMI panels, other PLCs, and field devices. When these CPUs receive specially crafted or malformed S7 packets, they fail to properly validate the packet structure, content, or authentication parameters. This validation failure creates a condition where the system cannot properly process legitimate communication traffic while simultaneously being vulnerable to malicious packet injection attacks. The vulnerability specifically impacts the protocol handling layer of the CPU firmware, where packet validation routines either completely fail or inadequately filter incoming data streams.
The operational impact of this vulnerability manifests as a Denial-of-Service condition that forces the affected CPU to enter a DEFECT operational mode. This state effectively renders the controller non-functional for industrial control purposes, requiring manual intervention to restore normal operation. The manual restart requirement creates significant operational disruption in environments where continuous operation is essential, potentially leading to production halts, safety system failures, or process control interruptions. In critical infrastructure scenarios, this vulnerability could result in extended downtime, financial losses, and potential safety hazards depending on the specific industrial application. The DEFECT mode persistence until manual intervention also means that automated recovery mechanisms cannot restore service, requiring on-site personnel or remote maintenance procedures that may not be immediately available.
Organizations should implement immediate mitigations including network segmentation to isolate affected controllers from untrusted networks, deployment of network access controls to filter S7 communication traffic, and regular firmware updates where available. The vulnerability aligns with CWE-129, which addresses improper validation of input data, and demonstrates characteristics consistent with ATT&CK technique T1499.004 related to network disruption. Industrial control system administrators should also consider implementing monitoring solutions to detect anomalous communication patterns that might indicate exploitation attempts. The affected systems require careful assessment of their operational environment and risk tolerance, particularly in scenarios where the manual restart requirement could create cascading failures or safety issues in process control environments. Regular security assessments and network traffic analysis should be conducted to identify potential exploitation attempts and ensure proper network isolation of critical control systems.