CVE-2016-9158 in SIMATIC S7-300 PN
Summary
by MITRE
A vulnerability has been identified in SIMATIC S7-300 CPU family (All versions), SIMATIC S7-300 CPU family (incl. related ET200 CPUs and SIPLUS variants) (All versions), SIMATIC S7-400 PN/DP V6 and below CPU family (incl. SIPLUS variants) (All versions), SIMATIC S7-400 PN/DP V7 CPU family (incl. SIPLUS variants) (All versions), SIMATIC S7-400 V6 and earlier CPU family (All versions), SIMATIC S7-400 V7 CPU family (All versions). Specially crafted packets sent to port 80/tcp could cause the affected devices to go into defect mode. A cold restart is required to recover the system.
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Analysis
by VulDB Data Team • 06/03/2026
The vulnerability identified as CVE-2016-9158 affects Siemens SIMATIC S7-300 PN CPUs and S7-400 PN CPUs across multiple firmware versions, representing a significant security concern for industrial control systems. This flaw resides within the network communication protocols of these programmable logic controllers, which are widely deployed in critical infrastructure environments including manufacturing plants, power generation facilities, and water treatment systems. The affected devices operate as part of the broader Siemens industrial automation ecosystem, where reliability and continuous operation are paramount for operational safety and business continuity.
The technical implementation of this vulnerability stems from insufficient input validation within the TCP/IP stack of the affected Siemens CPUs. Specifically, when these devices receive specially crafted packets on port 80/TCP, the system fails to properly handle malformed or unexpected data payloads, leading to an uncontrolled process termination or system crash. This behavior manifests as a denial of service condition that can be triggered remotely without requiring authentication or physical access to the device. The vulnerability exists at the protocol level where the system does not adequately sanitize incoming network traffic, creating a pathway for malicious actors to disrupt industrial processes through network-based attacks.
The operational impact of this vulnerability extends beyond simple service disruption, potentially affecting critical manufacturing processes, production line operations, and safety systems that depend on continuous PLC operation. In industrial environments where these controllers manage real-time process control, a denial of service condition could lead to production halts, quality control failures, or even safety hazards if the affected systems control critical safety mechanisms. The remote exploitation capability means that attackers can potentially target these devices from external networks, making them particularly dangerous in environments where industrial networks are not properly segmented from corporate IT infrastructure.
Organizations affected by this vulnerability should implement immediate mitigations including network segmentation to isolate affected devices from untrusted networks, deployment of network access control lists to restrict traffic to port 80/TCP, and regular monitoring for unusual network activity patterns. The vulnerability aligns with CWE-129, which addresses improper input validation in network protocols, and demonstrates characteristics consistent with ATT&CK technique T1499.004 for network denial of service attacks. Siemens has released firmware updates addressing this issue, and organizations should prioritize applying these patches while maintaining network monitoring capabilities to detect potential exploitation attempts. Additionally, implementing intrusion detection systems specifically configured to monitor for malformed TCP packets targeting these industrial control systems can provide early warning capabilities for potential attacks.