CVE-2017-8218 in TP-LINK
Summary
by MITRE
vsftpd on TP-Link C2 and C20i devices through firmware 0.9.1 4.2 v0032.0 Build 160706 Rel.37961n has a backdoor admin account with the 1234 password, a backdoor guest account with the guest password, and a backdoor test account with the test password.
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Analysis
by VulDB Data Team • 06/19/2022
The vulnerability identified as CVE-2017-8218 represents a critical security flaw in the vsftpd FTP server implementation on TP-Link C2 and C20i wireless routers. This backdoor account configuration exposes these network devices to unauthorized administrative access, creating a significant risk for network security and infrastructure integrity. The affected firmware versions 0.9.1 4.2 v0032.0 Build 160706 Rel.37961n demonstrate a persistent security weakness that allows attackers to gain elevated privileges without proper authentication mechanisms.
The technical implementation of this vulnerability involves hardcoded administrative credentials embedded within the firmware of these specific TP-Link router models. The presence of three distinct backdoor accounts with predetermined passwords creates multiple attack vectors for malicious actors. The 1234 password for the admin account, guest password for the guest account, and test password for the test account represent predictable authentication credentials that bypass normal security controls. This flaw directly violates fundamental security principles of credential management and access control, as it eliminates the need for legitimate authentication processes.
From an operational impact perspective, this vulnerability enables unauthorized remote access to network infrastructure, potentially allowing attackers to modify router configurations, intercept network traffic, or establish persistent access points within the network. The presence of backdoor accounts with default passwords creates a pathway for attackers to escalate privileges and gain complete control over the affected devices. Network administrators face significant challenges in detecting and mitigating this vulnerability since the accounts operate silently without normal authentication logs, making them particularly dangerous in enterprise environments.
The vulnerability aligns with CWE-798 (Use of Hard-coded Credentials) and CWE-259 (Use of Hard-coded Password) categories, demonstrating how hardcoded authentication information creates persistent security risks. From an ATT&CK framework perspective, this vulnerability maps to T1078 (Valid Accounts) and T1068 (Exploitation for Privilege Escalation), as attackers can leverage these pre-configured accounts to gain unauthorized access and elevate their privileges within the network infrastructure. The attack surface expands significantly as these backdoor accounts provide access to network configuration parameters, firewall settings, and routing information.
Mitigation strategies should prioritize immediate firmware updates to address the hardcoded credential issue, though the specific vulnerability affects older firmware versions that may no longer receive official updates. Network segmentation and access control measures can help limit the impact of potential exploitation, while regular security audits should verify that no unauthorized accounts exist on network devices. Security monitoring solutions should be configured to detect unusual authentication patterns and unauthorized access attempts. Organizations should implement comprehensive device inventory management to identify all affected TP-Link models and ensure proper patch management protocols are followed to prevent similar vulnerabilities from being introduced in future deployments.