CVE-2005-1680 in DSL-504T
Summary
by MITRE
D-Link DSL-502T, DSL-504T, DSL-562T, and DSL-G604T, when /cgi-bin/firmwarecfg is executed, allows remote attackers to bypass authentication (1) if their IP address already exists in /var/tmp/fw_ip or (2) if their request is the first, which causes /var/tmp/fw_ip to be created and contain their IP address.
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Analysis
by VulDB Data Team • 07/25/2017
The vulnerability described in CVE-2005-1680 represents a critical authentication bypass flaw affecting several D-Link DSL modem and router models including the DSL-502T, DSL-504T, DSL-562T, and DSL-G604T. This issue stems from improper authentication mechanisms within the firmware configuration web interface, specifically when processing requests to the /cgi-bin/firmwarecfg endpoint. The vulnerability manifests through two distinct but related attack vectors that collectively undermine the device's security posture and allow unauthorized remote access to administrative functions.
The technical implementation of this flaw involves the device's handling of IP address validation within the /var/tmp/fw_ip file. When an attacker sends a request to the vulnerable firmware configuration interface, the system checks whether the requesting IP address already exists in the /var/tmp/fw_ip file. If the IP address is present, the authentication bypass occurs without proper verification, allowing the attacker to access administrative functions. Additionally, if the attacker's request happens to be the first request to the system, the /var/tmp/fw_ip file gets created with their IP address, immediately enabling the bypass mechanism. This design flaw essentially creates a race condition and trust model that incorrectly assumes legitimate IP addresses are inherently trustworthy without proper authentication mechanisms.
The operational impact of this vulnerability is severe and multifaceted. Remote attackers can gain full administrative access to the affected routers without requiring valid credentials, enabling them to modify network configurations, change firewall rules, access network traffic, and potentially establish persistent backdoors. This vulnerability directly violates the principle of least privilege and authentication requirements that are fundamental to network security. The attack can be executed entirely remotely without any physical access or prior knowledge of administrative credentials, making it particularly dangerous for network administrators who may not be aware of the compromise. The vulnerability affects not just individual devices but entire networks that rely on these routers for connectivity and security enforcement.
This vulnerability maps to CWE-287, which describes improper authentication issues in software systems, specifically focusing on authentication bypass flaws that allow unauthorized access to protected resources. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under T1078 for Valid Accounts and T1021 for Remote Services, as the compromised device provides unauthorized access to network resources and services. The flaw demonstrates poor input validation and trust model implementation, where the system incorrectly assumes that IP address presence in a temporary file indicates legitimate authorization. Network security professionals should consider this vulnerability as part of broader router security assessments and implement proper network segmentation to limit the impact of such compromises.
The recommended mitigations for this vulnerability include immediate firmware updates from D-Link to address the authentication bypass flaw, implementing network access controls to restrict access to administrative interfaces, and deploying network monitoring solutions to detect unauthorized access attempts. Organizations should also consider disabling unnecessary administrative services, implementing strong network segmentation, and regularly auditing device configurations to ensure that authentication mechanisms remain intact. The vulnerability highlights the critical importance of proper authentication design and the dangers of relying on IP address validation as a security control mechanism, emphasizing the need for robust multi-factor authentication and proper access control implementations in network infrastructure devices.