CVE-2017-9492 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); Cisco DPC3939B (firmware version dpc3939b-v303r204217-150321a-CMCST); Cisco DPC3941T (firmware version DPC3941_2.5s3_PROD_sey); and Arris TG1682G (eMTA&DOCSIS version 10.0.132.SIP.PC20.CT, software version TG1682_2.2p7s2_PROD_sey) devices does not include the HTTPOnly flag in a Set-Cookie header for administration applications, which makes it easier for remote attackers to obtain potentially sensitive information via script access to cookies.
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Analysis
by VulDB Data Team • 12/29/2019
The vulnerability identified as CVE-2017-9492 affects multiple cable modem and gateway devices including Cisco DPC3939, DPC3939B, DPC3941T, and Arris TG1682G models. These devices operate with web-based administration interfaces that are accessible to users through standard web browsers. The core issue lies in the improper implementation of session management within the firmware's HTTP response headers, specifically the absence of the HTTPOnly flag in Set-Cookie headers. This critical flaw exists in firmware versions ranging from dpc3939-P20-18-v303r20421733-160420a-CMCST through various iterations of the affected device families. The vulnerability stems from the fact that when cookies are transmitted without the HTTPOnly flag, they become accessible to client-side scripting languages such as javascript, which creates an exploitable condition for malicious actors.
This technical weakness directly relates to CWE-1004 which describes the insufficient protection of sensitive cookies from client-side access. The absence of HTTPOnly flag in Set-Cookie headers creates a prime opportunity for cross-site scripting attacks, where attackers can leverage malicious scripts to steal session cookies and potentially gain unauthorized administrative access to the affected devices. The vulnerability operates at the application layer and specifically impacts the web administration interfaces of these devices, making it particularly dangerous as it allows remote attackers to exploit the flaw without requiring physical access or complex local privileges. The flaw essentially undermines the fundamental security principle of cookie isolation between server-side applications and client-side scripts, creating a pathway for session hijacking and unauthorized device control.
The operational impact of this vulnerability is significant for network administrators and end-users who rely on these devices for internet connectivity and network management. Attackers can exploit this weakness to establish persistent access to the device's web administration interface, potentially leading to complete device compromise. This compromise could enable attackers to modify network settings, redirect traffic, install malicious firmware, or use the device as a pivot point for attacking other systems within the local network. The vulnerability also poses risks to network security policies and compliance requirements, as it allows unauthorized access to sensitive network configuration data that should only be accessible to authorized administrators. The exposure is particularly concerning in enterprise and residential gateway environments where these devices serve as the primary connection point between internal networks and external internet services.
Mitigation strategies for CVE-2017-9492 should focus on immediate firmware updates from the device manufacturers as provided through official channels. Network administrators should implement network segmentation and access control measures to limit exposure of these devices to untrusted networks. Additional protective measures include monitoring network traffic for suspicious activities related to these devices, implementing web application firewalls to detect and block malicious scripts, and conducting regular security audits of networked devices. The vulnerability demonstrates the importance of proper cookie security implementation and aligns with ATT&CK technique T1212 which covers exploitation for credential access through web application vulnerabilities. Organizations should also consider implementing network monitoring solutions that can detect unauthorized access attempts and session hijacking activities, particularly in environments where these devices are deployed. The recommended approach combines both immediate remediation through vendor updates and ongoing security monitoring to prevent exploitation of this and similar vulnerabilities.