CVE-2014-6435 in DSL5018EN
Summary
by MITRE
cgi-bin/AZ_Retrain.cgi in Aztech ADSL DSL5018EN (1T1R), DSL705E, and DSL705EU devices does not check for authentication, which allows remote attackers to cause a denial of service (WAN connectivity reset) via a direct request.
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Analysis
by VulDB Data Team • 07/27/2024
The vulnerability identified as CVE-2014-6435 affects Aztech ADSL modem devices including the DSL5018EN (1T1R), DSL705E, and DSL705EU models. This represents a critical security flaw in the device's web-based management interface where the cgi-bin/AZ_Retrain.cgi script fails to implement proper authentication mechanisms. The flaw exists within the firmware of these networking devices, specifically targeting the administrative interface that controls WAN connectivity functions. The vulnerability stems from insufficient access control measures that allow any remote attacker to execute malicious requests without proper credentials, creating an unauthorized access vector that directly impacts network connectivity and device operation.
The technical implementation of this vulnerability resides in the absence of authentication checks within the AZ_Retrain.cgi script, which is designed to handle retraining operations for the ADSL connection. When an attacker sends a direct HTTP request to this unauthenticated endpoint, the device processes the request as if it were issued by an authorized administrator. This lack of authentication validation creates a path for remote exploitation where malicious actors can manipulate the device's WAN connection parameters. The script's design fails to validate user credentials, session tokens, or source IP addresses before executing the retraining functionality, which is typically used to reset or reconfigure the ADSL line settings. This flaw directly violates fundamental security principles of access control and authorization, making it a clear example of a CWE-285 vulnerability related to improper authorization.
The operational impact of this vulnerability is significant as it allows remote attackers to cause a denial of service condition by resetting the WAN connectivity on affected devices. When exploited, the vulnerability can result in complete network disruption for users relying on these modems for internet access, potentially affecting business operations and personal connectivity. The retraining function, when triggered without proper authentication, can cause the modem to reset its ADSL connection, effectively cutting off internet access for all connected devices. This type of attack can be particularly damaging in environments where continuous network availability is critical, such as small businesses, residential networks, or remote work setups. The attack requires minimal technical expertise to execute, making it a particularly dangerous vulnerability that can be exploited by automated tools or casual attackers.
From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1210 - Exploitation of Remote Services, where attackers leverage unauthenticated access to network services to manipulate device configurations. The flaw also represents a weakness in the principle of least privilege, as the device should only allow authenticated administrative access to critical functions. Organizations should implement immediate mitigations including network segmentation to isolate these devices from untrusted networks, disabling unnecessary services, and applying firmware updates from the vendor when available. The vulnerability highlights the importance of proper input validation and access control implementation in embedded systems, particularly in IoT and networking equipment where unauthorized access can have widespread operational consequences. Security practitioners should monitor for exploitation attempts and consider implementing network-based intrusion detection systems to identify unauthorized access attempts to administrative interfaces.