CVE-2017-9484 in DPC3939
Summary
by MITRE
The Comcast firmware on Cisco DPC3939 (firmware version dpc3939-P20-18-v303r20421733-160420a-CMCST) and DPC3939 (firmware version dpc3939-P20-18-v303r20421746-170221a-CMCST) devices allows remote attackers to discover a CM MAC address by sniffing Wi-Fi traffic and performing simple arithmetic calculations.
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Analysis
by VulDB Data Team • 11/02/2019
The vulnerability identified as CVE-2017-9484 affects Comcast firmware running on Cisco DPC3939 cable modem devices, specifically versions dpc3939-P20-18-v303r20421733-160420a-CMCST and dpc3939-P20-18-v303r20421746-170221a-CMCST. This security flaw represents a significant information disclosure vulnerability that compromises the confidentiality of network device identifiers. The issue stems from the firmware's improper handling of Wi-Fi traffic monitoring capabilities, allowing unauthorized parties to extract critical network information through passive reconnaissance techniques. The vulnerability is classified under CWE-200, which addresses "Information Exposure" and specifically relates to the unintentional disclosure of sensitive information to unauthorized actors.
The technical mechanism behind this vulnerability involves the analysis of Wi-Fi traffic patterns that contain embedded MAC address information within the communication protocols. Attackers can perform simple arithmetic calculations on captured network packets to derive the Cable Modem's MAC address without requiring any active exploitation or authentication credentials. This process exploits weaknesses in the firmware's packet processing and transmission methods, where the device's unique identifier becomes inadvertently exposed during normal network operations. The vulnerability operates at the network protocol level and demonstrates a fundamental flaw in how the firmware manages information flow between the device and its network environment, aligning with ATT&CK technique T1046 for Network Service Scanning and T1082 for System Information Discovery.
The operational impact of this vulnerability extends beyond simple information disclosure, as the MAC address serves as a critical identifier for network devices and can be used for further targeted attacks. Once an attacker obtains the CM MAC address, they can potentially correlate this information with other network reconnaissance activities, conduct targeted social engineering campaigns, or use it as part of more sophisticated attack vectors. The vulnerability affects the confidentiality aspect of the CIA triad, as it violates the principle that sensitive network information should remain protected from unauthorized access. Network administrators and security professionals must consider this vulnerability as a potential entry point for more comprehensive attacks, particularly in environments where cable modems serve as primary network access points for residential or small business users.
Mitigation strategies for CVE-2017-9484 should focus on firmware updates provided by Cisco and Comcast to address the specific implementation flaws in the affected versions. Network administrators should implement proper network segmentation to limit the exposure of sensitive information, while also monitoring for unusual traffic patterns that might indicate passive reconnaissance activities. The vulnerability highlights the importance of secure firmware development practices and proper information hiding mechanisms within network device implementations. Organizations should also consider implementing network traffic analysis tools that can detect and alert on anomalous packet patterns that might indicate attempts to exploit similar information disclosure vulnerabilities. This vulnerability serves as a reminder of the critical need for robust security testing and validation of network device firmware before deployment in production environments.