CVE-2017-9488 in DPC3939
Summary
by MITRE
The Comcast firmware on Cisco DPC3939 (firmware version dpc3939-P20-18-v303r20421746-170221a-CMCST) and DPC3941T (firmware version DPC3941_2.5s3_PROD_sey) devices allows remote attackers to access the web UI by establishing a session to the wan0 WAN IPv6 address and then entering unspecified hardcoded credentials. This wan0 interface cannot be accessed from the public Internet.
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Analysis
by VulDB Data Team • 11/02/2019
The vulnerability identified as CVE-2017-9488 affects Comcast firmware versions running on Cisco DPC3939 and DPC3941T modem devices, representing a critical security flaw in consumer-grade networking equipment. This issue stems from hardcoded authentication credentials that persistently grant unauthorized remote access to the device's web-based management interface. The vulnerability specifically impacts the wan0 WAN IPv6 address interface, which serves as a potential attack vector for malicious actors seeking to compromise connected networks. The affected firmware versions demonstrate a fundamental flaw in credential management where default authentication parameters remain unchanged and easily discoverable by attackers. This weakness creates a persistent backdoor access mechanism that bypasses normal authentication procedures and allows attackers to assume administrative control of the modem without requiring legitimate credentials or network access privileges.
The technical implementation of this vulnerability involves hardcoded credentials embedded within the firmware image, creating a persistent authentication mechanism that cannot be modified or removed through standard administrative procedures. According to CWE-259, this represents a weakness in authentication mechanisms where hardcoded credentials are used instead of dynamic authentication tokens or properly managed credential storage. The vulnerability operates through the wan0 interface which, while not directly accessible from the public internet, can be reached through internal network traversal or compromised intermediate systems. The IPv6 address configuration provides attackers with a direct pathway to the device's management interface, enabling them to perform administrative operations including configuration changes, traffic monitoring, and potential network disruption. The device's inability to properly authenticate users through standard mechanisms while maintaining these hardcoded credentials creates an inherent security risk that persists across device reboots and firmware updates.
The operational impact of this vulnerability extends beyond simple unauthorized access to encompass potential network compromise and data exfiltration capabilities. Attackers who successfully exploit this vulnerability can manipulate the modem's routing configurations, potentially redirecting traffic through malicious intermediaries or blocking legitimate network communications. The presence of administrative access through hardcoded credentials allows for persistent backdoor establishment, enabling long-term network surveillance and potential lateral movement within compromised networks. According to ATT&CK framework technique T1071.004, this vulnerability enables adversaries to conduct network protocol manipulation and can be leveraged for information gathering and command and control operations. The vulnerability affects not only individual device security but also represents a potential threat to broader network infrastructure, particularly in environments where multiple affected devices exist. Network administrators face challenges in identifying compromised devices since the attack vector remains hidden from standard network monitoring tools and does not generate typical authentication failure logs.
Mitigation strategies for CVE-2017-9488 require immediate firmware updates from Cisco and Comcast to address the hardcoded credential issue. Organizations should implement network segmentation to isolate affected devices from critical network segments and consider disabling unused interfaces including the wan0 IPv6 interface when not actively required. Network monitoring solutions should be enhanced to detect unusual traffic patterns originating from the wan0 interface or unauthorized access attempts to device management interfaces. Device administrators should regularly audit network configurations and verify that default credentials have been changed or disabled across all network equipment. The vulnerability highlights the importance of proper credential management and secure firmware deployment practices, emphasizing that hardcoded credentials should never be present in production network equipment. Additionally, network administrators should consider implementing intrusion detection systems that can identify and alert on unauthorized access attempts to device management interfaces, particularly those that might leverage hardcoded credential vulnerabilities. Regular vulnerability assessments and firmware update schedules should be established to ensure that similar security flaws are identified and remediated before they can be exploited by malicious actors.