CVE-2017-9482 in DPC3939
Summary
by MITRE
The Comcast firmware on Cisco DPC3939 (firmware version dpc3939-P20-18-v303r20421746-170221a-CMCST) devices allows remote attackers to obtain root access to the Network Processor (NP) Linux system by enabling a TELNET daemon (through CVE-2017-9479 exploitation) and then establishing a TELNET session.
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Analysis
by VulDB Data Team • 11/02/2019
The vulnerability identified as CVE-2017-9482 represents a critical security flaw in Cisco DPC3939 residential gateway devices running specific Comcast firmware versions. This issue demonstrates how seemingly isolated vulnerabilities can combine to create severe remote access capabilities for malicious actors. The affected devices operate with a Network Processor (NP) Linux system that serves as a separate execution environment from the main gateway firmware, creating a potential attack surface that extends beyond typical router security boundaries.
The technical exploitation pathway begins with CVE-2017-9479, which allows attackers to enable a TELNET daemon on the device without proper authentication. This vulnerability typically stems from insufficient input validation or improper privilege management within the device's configuration interfaces. Once the TELNET daemon is activated, attackers can establish a remote session with the Network Processor Linux system, bypassing normal security controls and gaining access to a privileged execution environment. The Network Processor operates with root-level privileges, making this access particularly dangerous as it provides direct control over system functions, network interfaces, and potentially sensitive data processing capabilities.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it enables attackers to manipulate the device's core networking functions, modify system configurations, and potentially use the device as a pivot point for broader network attacks. The TELNET protocol, while designed for remote administration, lacks modern encryption and authentication mechanisms, making it particularly susceptible to interception and exploitation. This vulnerability affects a significant number of residential and small office gateway devices, creating a substantial attack surface for threat actors who may leverage this access for data exfiltration, network reconnaissance, or to establish persistent backdoors within the network infrastructure.
Security professionals should note that this vulnerability aligns with CWE-284 (Improper Access Control) and CWE-310 (Cryptographic Issues) categories, as it demonstrates both inadequate privilege management and the use of insecure communication protocols. The attack pattern follows typical MITRE ATT&CK framework techniques including T1075 (Password Filter DLL) and T1059 (Command and Scripting Interpreter) for establishing persistent access and executing commands. Organizations should implement immediate mitigations including firmware updates, network segmentation, and monitoring for unauthorized TELNET connections, while also considering the broader implications of unpatched embedded device vulnerabilities in their network security posture.