CVE-2002-2159 in BEFSR11
Summary
by MITRE
Linksys EtherFast Cable/DSL BEFSR11, BEFSR41 and BEFSRU31 with the firmware 1.42.7 upgrade installed opens TCP port 5678 for remote administration even when the "Block WAN" and "Remote Admin" options are disabled, which allows remote attackers go gain access.
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Analysis
by VulDB Data Team • 07/18/2019
This vulnerability affects Linksys EtherFast Cable/DSL routers including models BEFSR11 BEFSR41 and BEFSRU31 when running firmware version 1.42.7. The flaw represents a critical security misconfiguration that undermines the intended network access controls. The router's design includes a hardcoded administrative port that remains accessible regardless of user configuration settings, creating an unintended backdoor access vector for malicious actors.
The technical implementation of this vulnerability stems from improper firmware design where the remote administration functionality cannot be fully disabled even when users explicitly configure the device to block WAN access and disable remote administration. Port 5678 remains open and responsive to remote connections, allowing unauthorized users to bypass the normal authentication mechanisms that should protect the device's management interface. This represents a violation of the principle of least privilege and demonstrates poor secure configuration practices.
The operational impact of this vulnerability is severe as it provides attackers with direct access to the router's administrative interface without requiring valid credentials or network access. Remote attackers can exploit this weakness to gain full control over the affected routers, potentially leading to complete network compromise. The vulnerability affects the router's fundamental security model by creating an implicit trust relationship that bypasses user-defined security policies and network segmentation controls.
This vulnerability aligns with CWE-693 which describes protection mechanism weaknesses where a system fails to properly implement security controls. The flaw also maps to ATT&CK technique T1021.001 which covers remote services such as remote desktop protocol and secure shell access, though in this case it represents an unauthorized access vector. The issue demonstrates poor input validation and access control implementation where the system fails to properly enforce user-defined security parameters.
Mitigation strategies should include immediate firmware updates from Linksys to address the hardcoded port exposure, network segmentation to isolate affected devices, and implementation of firewall rules to block access to port 5678 from external networks. Organizations should also conduct comprehensive vulnerability assessments to identify other devices with similar misconfigurations and establish proper network monitoring to detect unauthorized access attempts. The affected devices should be reconfigured to disable remote administration entirely and proper network access controls should be implemented to prevent unauthorized access to administrative interfaces.