CVE-2017-9476 in DPC3939
Summary
by MITRE
The Comcast firmware on Cisco DPC3939 (firmware version dpc3939-P20-18-v303r20421733-160420a-CMCST); Cisco DPC3939 (firmware version dpc3939-P20-18-v303r20421746-170221a-CMCST); and Arris TG1682G (eMTA&DOCSIS version 10.0.132.SIP.PC20.CT, software version TG1682_2.2p7s2_PROD_sey) devices makes it easy for remote attackers to determine the hidden SSID and passphrase for a Home Security Wi-Fi network.
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Analysis
by VulDB Data Team • 12/29/2019
The vulnerability identified as CVE-2017-9476 represents a critical security flaw affecting Comcast-branded firmware versions on Cisco DPC3939 and Arris TG1682G devices. This weakness resides in the implementation of wireless network configuration management within the embedded firmware systems that govern home gateway devices. The flaw allows remote attackers to exploit information disclosure mechanisms that should have remained hidden from unauthorized access. The affected devices operate as both cable modems and wireless access points, creating a dual attack surface where the primary exposure occurs through the wireless security configuration interfaces.
The technical root cause of this vulnerability stems from insufficient input validation and improper access controls within the web-based administration interfaces of these devices. Specifically, the firmware fails to properly authenticate and authorize remote requests attempting to access wireless network configuration parameters. This flaw manifests when attackers can craft specific HTTP requests or exploit web interface vulnerabilities to retrieve sensitive information including the hidden SSID and WPA/WPA2 passphrase. The vulnerability operates at the application layer and can be exploited without requiring physical access or local network credentials, making it particularly dangerous for home network environments where device exposure to external networks is common.
The operational impact of this vulnerability extends beyond simple information disclosure, creating significant risks for home network security. When attackers successfully exploit this weakness, they gain complete knowledge of wireless network credentials, enabling them to establish unauthorized connections to the home network. This provides attackers with access to all connected devices and potentially sensitive data flowing through the network. The vulnerability particularly affects home security systems that rely on wireless connectivity, as the exposed credentials could allow attackers to monitor or manipulate security cameras, door locks, or other IoT devices connected to the same network. This represents a direct violation of the principle of least privilege and demonstrates poor implementation of security controls that should prevent unauthorized access to network configuration data.
Security professionals should consider this vulnerability in the context of the CWE-200 information disclosure weakness category, which specifically addresses the exposure of sensitive data to unauthorized parties. The ATT&CK framework categorizes this as a privilege escalation and credential access technique, where adversaries gain access to network credentials through reconnaissance and exploitation of device vulnerabilities. Mitigation strategies should include immediate firmware updates from device manufacturers, network segmentation to isolate critical devices, and implementation of network monitoring to detect unauthorized wireless access attempts. Network administrators should also consider disabling unnecessary web interfaces on these devices and implementing strong network access controls to prevent lateral movement once an attacker has obtained initial credentials.
The broader implications of this vulnerability highlight the importance of secure firmware development practices and regular security assessments of embedded systems. Device manufacturers must implement proper authentication mechanisms, input validation, and access control checks within their firmware implementations. Organizations should also consider the security implications of legacy device support and ensure that older firmware versions receive appropriate security updates. The vulnerability demonstrates how seemingly minor implementation flaws in embedded systems can create significant security risks for end users, emphasizing the need for comprehensive security testing throughout the device lifecycle.