CVE-2018-16557 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). Sending of specially crafted packets to port 102/tcp via Ethernet interface via PROFIBUS or Multi Point Interfaces (MPI) could cause a Denial-of-Service condition on affected devices. Flashing with a firmware image may be required to recover the CPU. Successful exploitation requires an attacker to have network access to port 102/tcp via Ethernet interface or to be able to send messages via PROFIBUS or Multi Point Interfaces (MPI) to the device. No user interaction is required. If no access protection is configured, no 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 with specific firmware versions. The flaw resides in the handling of specially crafted packets sent to port 102/tcp through Ethernet interfaces or PROFIBUS/MPI communication channels. This represents a critical security weakness that can be exploited to cause denial-of-service conditions without requiring any user interaction or elevated privileges when no access protection is configured. The vulnerability impacts a wide range of industrial control systems that rely on these PLC models for critical automation processes. According to the ATT&CK framework, this vulnerability aligns with the T1499.004 technique related to network disruption and the T1566.001 technique for malicious code delivery through network protocols. The CWE classification for this issue would be CWE-129, representing an insufficient input validation or improper restriction of operations within a recognized operating range, which is commonly exploited in industrial control system environments.
The technical implementation of this vulnerability involves sending malformed or specially crafted packets to the target device's port 102/tcp, which is the standard port used for ISO-on-TCP communication in industrial environments. When these packets are processed by the affected PLC firmware, they trigger an unexpected behavior that leads to system instability and potential complete system shutdown. The exploitation mechanism does not require any authentication or privilege escalation since the vulnerability exists in the protocol handling layer itself. This makes it particularly dangerous in operational technology environments where physical access might be limited but network access can be achieved through various means including compromised devices or network infiltration. The lack of user interaction requirement means that an attacker could potentially cause widespread disruption by simply sending malicious packets to the network without needing to establish a connection or perform any complex attack procedures.
The operational impact of this vulnerability extends beyond simple system unavailability as it can compromise the core functionality of the CPU and potentially affect entire production lines or critical infrastructure operations. The recovery process requires flashing a new firmware image which can result in significant downtime and potential data loss during the recovery phase. This disruption can have cascading effects on industrial processes that depend on these PLCs for real-time control and monitoring. The vulnerability affects multiple generations of Siemens PLCs, indicating a widespread issue that requires coordinated remediation efforts across industrial installations. Organizations relying on these devices for critical infrastructure operations face significant risk of operational disruption, especially since the vulnerability can be exploited remotely without requiring physical access to the devices. The absence of known public exploitation at the time of advisory publication does not diminish the severity, as this vulnerability represents a latent threat that could be weaponized by threat actors with access to industrial control systems.
Mitigation strategies for this vulnerability should include immediate network segmentation and access control measures to restrict access to port 102/tcp and the affected PLCs. Organizations should implement network access controls using firewalls to block unauthorized access to the target ports and consider disabling unnecessary network services on these devices. The recommended solution involves applying the latest firmware updates provided by Siemens to address the specific vulnerability in the protocol handling mechanism. Additionally, monitoring network traffic for suspicious patterns on port 102/tcp can help detect potential exploitation attempts. Security teams should also implement intrusion detection systems that can identify anomalous communication patterns associated with this vulnerability. Regular security assessments of industrial control systems should include verification of firmware versions and implementation of network access controls to prevent unauthorized access to critical industrial devices. The vulnerability underscores the importance of maintaining current firmware versions and implementing proper network segmentation practices to protect industrial control systems from remote exploitation.