CVE-2017-9477 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 the CM MAC address by connecting to the device's xfinitywifi hotspot.
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Analysis
by VulDB Data Team • 11/02/2019
The vulnerability described in CVE-2017-9477 represents a significant security flaw in Cisco DPC3939 cable modem devices running specific Comcast firmware versions. This issue affects the device's wireless hotspot functionality, specifically the xfinitywifi service that is automatically enabled on these modems. The vulnerability stems from improper access control mechanisms within the device's web interface, which fails to adequately protect sensitive network information from unauthorized discovery. The flaw allows remote attackers to obtain the cable modem's cable modem MAC address through simple network connectivity to the device's hotspot service, bypassing normal authentication requirements that should protect such critical information.
The technical implementation of this vulnerability involves the device's wireless access point configuration where the xfinitywifi hotspot service exposes network identification information without proper authorization checks. When attackers connect to the device's wireless network, they can access the web-based management interface through unauthenticated pathways that reveal the CM MAC address. This occurs because the device's firmware does not properly implement access controls for the hotspot management functions, allowing any network user to retrieve the device's unique hardware identifier. The vulnerability specifically affects firmware versions dpc3939-P20-18-v303r20421733-160420a-CMCST and dpc3939-P20-18-v303r20421746-170221a-CMCST, indicating that the flaw was present in these particular firmware releases but may have been addressed in subsequent versions.
The operational impact of this vulnerability extends beyond simple information disclosure, as the CM MAC address serves as a critical identifier in cable network infrastructure that can be leveraged for further attacks. The exposure of this hardware identifier enables attackers to perform network reconnaissance and potentially map the topology of cable network deployments. According to CWE-200, this represents a weakness in information disclosure where sensitive information about the device's hardware configuration is exposed to unauthorized parties. The vulnerability also aligns with ATT&CK technique T1046 which involves network service scanning and reconnaissance activities that attackers can use to gather information about target systems before launching more sophisticated attacks.
The implications of this vulnerability are particularly concerning for cable network security as the CM MAC address can be used to identify specific devices within the network infrastructure, potentially enabling attackers to target specific modems or perform device-specific attacks. This information disclosure can facilitate various attack vectors including device impersonation, targeted denial-of-service attacks, or more sophisticated reconnaissance activities that could lead to privilege escalation within the network. The vulnerability demonstrates a fundamental flaw in the device's security architecture where sensitive network identification information is exposed through wireless access points that should be restricted to authorized users only. Organizations should consider implementing network segmentation and access controls to limit the exposure of such information and ensure that wireless access points on network devices are properly secured with strong authentication mechanisms.
Mitigation strategies for this vulnerability should include immediate firmware updates to versions that address the access control flaws, proper network segmentation to isolate wireless access points from critical network infrastructure, and implementation of wireless network monitoring to detect unauthorized access attempts. Network administrators should also consider disabling unnecessary wireless services on network devices when they are not required for legitimate operations. The vulnerability highlights the importance of proper access control implementation in network device firmware and underscores the need for comprehensive security testing of network infrastructure components. Organizations should also implement regular security assessments of their network devices to identify similar information disclosure vulnerabilities that could compromise network security.