CVE-2015-8738 in Wireshark
Summary
by MITRE
The s7comm_decode_ud_cpu_szl_subfunc function in epan/dissectors/packet-s7comm_szl_ids.c in the S7COMM dissector in Wireshark 2.0.x before 2.0.1 does not validate the list count in an SZL response, which allows remote attackers to cause a denial of service (divide-by-zero error and application crash) via a crafted packet.
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Analysis
by VulDB Data Team • 07/02/2022
The vulnerability CVE-2015-8738 resides within the S7COMM dissector component of Wireshark, specifically in the s7comm_decode_ud_cpu_szl_subfunc function located at epan/dissectors/packet-s7comm_szl_ids.c. This flaw affects Wireshark versions 2.0.x prior to 2.0.1 and represents a critical denial of service vulnerability that can be exploited remotely. The S7COMM protocol is widely used for communication between Siemens programmable logic controllers and other devices in industrial control systems, making this vulnerability particularly concerning for operational technology environments. The vulnerability stems from inadequate input validation within the protocol dissector, which is responsible for parsing and analyzing S7COMM traffic for network forensic analysis.
The technical implementation of this vulnerability occurs when the s7comm_decode_ud_cpu_szl_subfunc function processes SZL (System Data List) responses from Siemens S7 systems. The function fails to properly validate the list count parameter contained within these responses, which can be manipulated by an attacker to contain a zero value. When Wireshark attempts to process this malformed data during packet analysis, it triggers a divide-by-zero error in the application's memory handling routines. This mathematical error occurs because the code attempts to perform division operations using the invalid list count value as a divisor, leading to immediate application termination and system crash. The vulnerability is classified as a divide-by-zero error under CWE-369 and represents a classic example of improper input validation in network protocol parsing components.
The operational impact of CVE-2015-8738 extends beyond simple service disruption to potentially compromise network monitoring capabilities in industrial environments. When exploited, this vulnerability can cause Wireshark to crash, effectively removing the network analysis tool from service and potentially masking actual network anomalies or malicious activities. In operational technology contexts where Wireshark is used for network security monitoring and troubleshooting, such a crash could result in critical blind spots during security incidents. The vulnerability maps to ATT&CK technique T1498.001 (Network Denial of Service) and can be categorized under the broader ATT&CK tactic of Impact. Organizations relying on Wireshark for network traffic analysis in critical infrastructure environments face significant risk, as the attack requires no authentication and can be executed by any remote network entity capable of sending crafted S7COMM packets.
Mitigation strategies for CVE-2015-8738 center on immediate software updates and network segmentation measures. The primary solution involves upgrading to Wireshark version 2.0.1 or later, where the vulnerability has been patched through proper input validation of the list count parameter in the affected function. Network administrators should also implement traffic filtering measures to restrict S7COMM traffic where possible, particularly in environments where such protocols are not essential for operations. The vulnerability demonstrates the importance of robust input validation in protocol dissectors and highlights the need for security testing of network analysis tools that process potentially malicious traffic. Organizations should also consider implementing network monitoring solutions that can detect and alert on protocol anomalies, providing additional defense in depth against similar vulnerabilities. Security teams should conduct regular vulnerability assessments of network analysis tools and maintain updated threat intelligence regarding protocol-specific vulnerabilities in industrial control systems.