CVE-2017-9489 in DPC3939B
Summary
by MITRE
The Comcast firmware on Cisco DPC3939B (firmware version dpc3939b-v303r204217-150321a-CMCST) devices allows configuration changes via CSRF.
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Analysis
by VulDB Data Team • 11/02/2019
The vulnerability identified as CVE-2017-9489 affects Cisco DPC3939B modem devices running specific firmware versions including dpc3939b-v303r204217-150321a-CMCST. This represents a critical security flaw that enables unauthorized modification of device configuration parameters through Cross-Site Request Forgery attacks. The issue stems from the absence of proper authentication mechanisms and anti-CSRF protections within the web-based management interface of these devices, making them susceptible to exploitation by malicious actors who can manipulate the device settings without proper authorization. The vulnerability specifically targets the configuration change functionality of the Comcast firmware that is embedded in these Cisco devices, creating a significant risk to network security and device integrity.
The technical flaw manifests in the web interface implementation where configuration requests lack proper CSRF token validation. When a user accesses the device management portal, the system does not adequately verify that requests originate from legitimate administrative sessions rather than forged requests. This weakness allows attackers to craft malicious web pages or send specially crafted requests that, when executed by an authenticated user, will modify device settings without the user's knowledge or consent. The flaw exists because the firmware fails to implement standard CSRF protection mechanisms such as token generation, validation, and session management that are essential for preventing unauthorized configuration changes. This vulnerability is classified under CWE-352 which specifically addresses Cross-Site Request Forgery issues in web applications and systems, making it a well-documented and widely recognized security weakness.
The operational impact of this vulnerability extends beyond simple configuration changes and can lead to severe consequences for network security and device functionality. An attacker could potentially disable security features, modify network settings, redirect traffic, or even establish persistent backdoors within the device. The affected devices are commonly deployed in residential and small business environments, making them attractive targets for cybercriminals seeking to gain unauthorized access to networks or disrupt services. The vulnerability also creates opportunities for attackers to escalate their privileges and potentially compromise the entire network infrastructure that relies on these modems as gateways. This type of vulnerability is particularly dangerous because it can be exploited through social engineering tactics where users are tricked into visiting malicious websites that automatically submit configuration change requests to the vulnerable device, as outlined in the ATT&CK framework under T1072 for Application Deployment Software.
Mitigation strategies for CVE-2017-9489 should prioritize immediate firmware updates from Cisco and Comcast to address the CSRF implementation flaws. Network administrators should also implement network segmentation to limit access to these devices and establish strict access controls for administrative interfaces. Additional protective measures include disabling unnecessary web management interfaces, implementing network monitoring to detect unauthorized configuration changes, and conducting regular security assessments of networked devices. The vulnerability demonstrates the critical importance of proper authentication and authorization mechanisms in embedded systems and underscores the need for manufacturers to implement comprehensive security testing throughout the development lifecycle. Organizations should also consider implementing security awareness training to help users recognize potential social engineering attacks that could exploit this vulnerability.