CVE-2020-29138 in F@ST3486 NET DOCSIS
Summary
by MITRE • 11/27/2020
Incorrect Access Control in the configuration backup path in SAGEMCOM F@ST3486 NET DOCSIS 3.0, software NET_4.109.0, allows remote unauthenticated users to download the router configuration file via the /backupsettings.conf URI, when any valid session is running.
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Analysis
by VulDB Data Team • 12/11/2020
The vulnerability described in CVE-2020-29138 represents a critical access control flaw within the SAGEMCOM F@ST3486 NET DOCSIS 3.0 router firmware version NET_4.109.0. This issue stems from improper authorization checks in the router's web interface configuration backup functionality, specifically affecting the /backupsettings.conf URI endpoint. The flaw allows remote attackers to bypass authentication mechanisms and download sensitive router configuration files without requiring valid credentials or active sessions, creating a significant security risk for network infrastructure deployments.
The technical implementation of this vulnerability exploits a weakness in the router's authentication model where the backup configuration path does not properly validate user credentials or session state before granting access to sensitive system files. This misconfiguration enables attackers to directly access the /backupsettings.conf endpoint and retrieve the complete router configuration, which typically contains critical network parameters including administrative credentials, network settings, firewall rules, and other sensitive operational data. The vulnerability is particularly concerning because it can be exploited even when a valid session is active, meaning that legitimate users' sessions do not provide protection against this unauthorized access vector.
The operational impact of this vulnerability extends beyond simple information disclosure, as the downloaded configuration files can provide attackers with comprehensive insights into the network infrastructure. These configuration files often contain administrator passwords, network topology information, and security policies that could be leveraged for further attacks within the network. The vulnerability creates a persistent risk for organizations relying on these devices, as the exposure remains active until the firmware is updated or the device is physically secured. Network reconnaissance activities can easily identify affected devices through standard scanning techniques, making this vulnerability particularly attractive to automated attack tools.
Security professionals should consider this vulnerability in the context of CWE-284, which addresses improper access control issues in software systems. The flaw also aligns with ATT&CK technique T1213.002, which covers data from information repositories, as attackers can extract sensitive configuration data from the affected devices. Organizations should prioritize immediate remediation through firmware updates provided by SAGEMCOM, implement network segmentation to limit access to administrative interfaces, and consider deploying intrusion detection systems to monitor for access attempts to the vulnerable URI endpoint. Additionally, network administrators should review and restrict access to administrative interfaces, implement strong authentication mechanisms, and conduct regular vulnerability assessments to identify similar access control weaknesses in other network infrastructure components.
The broader implications of this vulnerability highlight the importance of proper input validation and access control implementation in network device firmware development. This flaw demonstrates how seemingly minor configuration issues can create significant security risks, particularly in widely deployed consumer and enterprise networking equipment. Organizations should maintain current threat intelligence feeds to identify similar vulnerabilities in their network infrastructure and implement comprehensive security monitoring to detect unauthorized access attempts to administrative interfaces. Regular firmware updates and security audits remain essential practices for maintaining network security posture against such persistent threats.