CVE-2017-9491 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 set the secure flag for cookies in an https session to an administration application, which makes it easier for remote attackers to capture these cookies by intercepting their transmission within an http session.
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Analysis
by VulDB Data Team • 12/29/2019
The vulnerability described in CVE-2017-9491 affects multiple cable modem and gateway devices including Cisco DPC3939, DPC3939B, DPC3941T, and Arris TG1682G models. These devices operate as part of the broader consumer gateway infrastructure that provides internet connectivity and manages various network services including DOCSIS provisioning and management interfaces. The affected firmware versions demonstrate a critical configuration flaw in how the web-based administration interfaces handle session management and cookie security. This vulnerability specifically impacts the security of HTTPS sessions used for administrative access to these devices, creating a significant risk for unauthorized access and data interception.
The technical flaw manifests in the improper implementation of cookie security mechanisms within the web administration interfaces of these devices. When users access the administrative web interface over HTTPS, the firmware fails to properly set the secure flag on cookies that are transmitted between the client browser and the device's web server. The secure flag is a critical HTTP cookie attribute that ensures cookies are only transmitted over encrypted HTTPS connections and are never sent over unencrypted HTTP connections. Without this flag, cookies can be intercepted and captured during transmission, particularly when users might inadvertently navigate to HTTP versions of the interface or when network traffic is intercepted through man-in-the-middle attacks. This weakness directly violates security best practices outlined in the OWASP Top Ten and represents a specific implementation of CWE-614, which addresses insecure cookie handling in web applications.
The operational impact of this vulnerability extends beyond simple credential theft to encompass potential full device compromise and network infiltration. Remote attackers can exploit this weakness to capture administrative session cookies, which would allow them to impersonate legitimate administrators and gain unauthorized access to the device configuration interfaces. This could enable attackers to modify network settings, change user credentials, disable security features, or even redirect traffic through malicious proxies. The vulnerability is particularly dangerous because it affects devices deployed in home and small office environments where network security monitoring may be minimal, and users often connect to untrusted networks. According to ATT&CK framework techniques, this vulnerability maps to T1071.004 for application layer protocol usage and T1566 for credential access through network sniffing and interception methods.
Mitigation strategies for this vulnerability require immediate firmware updates from device manufacturers, as the flaw is inherent to specific firmware versions and cannot be resolved through configuration changes alone. Network administrators and users should prioritize updating all affected devices to the latest firmware versions that properly implement secure cookie flags. Additional defensive measures include implementing network segmentation to isolate these devices from critical network segments, deploying network monitoring tools to detect unusual traffic patterns, and ensuring that administrative access is restricted to trusted networks only. The vulnerability demonstrates the importance of proper cookie security implementation in embedded web interfaces and highlights the need for comprehensive security testing of network device firmware, particularly for administrative interfaces that handle sensitive configuration data. Organizations should also consider implementing additional authentication mechanisms such as two-factor authentication for administrative access and regular security assessments of their network infrastructure to identify similar configuration weaknesses.