CVE-2018-16556 in SIMATIC S7-400
Summary
by MITRE
A vulnerability has been identified in SIMATIC S7-400 (incl. F) V6 and below (All versions), SIMATIC S7-400 PN/DP V7 (incl. F) (All versions), SIMATIC S7-400H V4.5 and below (All versions), SIMATIC S7-400H V6 (All versions), SIMATIC S7-410 (All versions < V8.2.1). Specially crafted packets sent to port 102/tcp via Ethernet interface, via PROFIBUS, or via Multi Point Interfaces (MPI) could cause the affected devices to go into defect mode. Manual reboot is required to resume normal operation. Successful exploitation requires an attacker to be able to send specially crafted packets to port 102/tcp via Ethernet interface, via PROFIBUS or Multi Point Interfaces (MPI). No user interaction and no user privileges are required to exploit the security vulnerability. The vulnerability could allow causing a Denial-of-Service condition of the core functionality of the CPU, compromising the availability of the system. At the time of advisory publication no public exploitation of this security vulnerability was known.
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Analysis
by VulDB Data Team • 06/19/2023
This vulnerability affects Siemens SIMATIC S7-400 series PLCs including various models such as S7-400, S7-400 PN/DP, S7-400H, and S7-410 devices running firmware versions up to and including V6. The flaw resides in the handling of packets sent to port 102/tcp which is the standard port for ISO on TCP protocol used in industrial communication. This vulnerability represents a critical denial-of-service condition that can render the affected industrial control systems non-operational. The issue is classified under CWE-121 as a buffer overflow condition, though the specific manifestation involves improper packet processing that leads to system instability rather than traditional memory corruption. The attack vector is particularly concerning because it can be exploited through multiple communication interfaces including Ethernet, PROFIBUS, and Multi Point Interfaces (MPI) without requiring any user interaction or authentication privileges, making it highly accessible to potential attackers.
The operational impact of CVE-2018-16556 extends beyond simple service disruption to potentially compromise the availability of critical industrial processes. When exploited, the vulnerability forces affected devices into a defect mode where the CPU core functionality becomes compromised, requiring manual reboot to restore normal operation. This type of attack directly maps to the ATT&CK technique T1499.004 for network denial-of-service attacks, specifically targeting industrial control systems. The vulnerability affects devices that are fundamental to industrial automation and control systems, particularly those in critical infrastructure sectors such as manufacturing, power generation, and water treatment facilities. The lack of user interaction requirements makes this vulnerability particularly dangerous as it can be exploited remotely by attackers who have network access to the affected devices or through adjacent network segments.
Mitigation strategies for this vulnerability should focus on network segmentation and access control measures to prevent unauthorized access to the affected industrial networks. The most effective immediate solution involves implementing network access controls to block traffic to port 102/tcp from untrusted sources, particularly in environments where physical security cannot be guaranteed. Organizations should also consider applying firmware updates from Siemens as soon as they become available, though the vulnerability's nature suggests that even patching might not fully resolve the issue without proper network isolation. Network monitoring should be enhanced to detect unusual traffic patterns on port 102/tcp that might indicate exploitation attempts. The vulnerability's classification as a denial-of-service condition means that traditional intrusion detection systems might not immediately flag the attack, requiring specialized monitoring for industrial protocols. This aligns with the ATT&CK framework's emphasis on defensive measures against industrial control system attacks through network segmentation and access control. Additionally, implementing network access control lists and ensuring that only authorized devices can communicate with the affected PLCs through the relevant interfaces provides a layered defense approach that addresses the multiple attack vectors identified in the vulnerability.