CVE-2021-20163 in AC2600 TEW-827DRU
Summary
by MITRE • 12/31/2021
Trendnet AC2600 TEW-827DRU version 2.08B01 leaks information via the ftp web page. Usernames and passwords for all ftp users are revealed in plaintext on the ftpserver.asp page.
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Analysis
by VulDB Data Team • 01/05/2022
The vulnerability identified as CVE-2021-20163 affects Trendnet AC2600 TEW-827DRU routers running firmware version 2.08B01 and represents a critical information disclosure flaw that directly violates security best practices. This vulnerability stems from improper input validation and output sanitization within the web interface's ftp server configuration page, specifically the ftpserver.asp component. The flaw allows unauthenticated attackers to access sensitive authentication credentials through a simple web request, creating a significant risk for network security.
The technical implementation of this vulnerability resides in the web application layer where the router's firmware fails to properly sanitize output data before rendering it to web clients. When users navigate to the ftp server configuration page, the application directly includes plaintext credentials in the HTML response without any form of access control or authentication verification. This represents a classic case of insecure direct object reference and improper access control, as defined by CWE-284 and CWE-20. The vulnerability operates at the application layer and can be exploited through standard web browser interactions, requiring no specialized tools or privileges beyond basic network access to the affected device.
The operational impact of this vulnerability extends far beyond simple credential exposure, as it provides attackers with direct access to the router's file transfer protocol services. Once compromised, attackers can leverage these credentials to gain unauthorized access to the router's file system, potentially enabling them to modify configuration settings, install malicious firmware, or use the device as a pivot point for further attacks within the network. This vulnerability directly aligns with ATT&CK technique T1078.004 which covers valid accounts and T1566.001 which involves credential harvesting through social engineering. The exposure of plaintext credentials also violates security principles outlined in NIST SP 800-63B regarding authentication and session management.
Mitigation strategies for this vulnerability require immediate firmware updates from Trendnet to address the underlying code execution flaw and proper output sanitization. Network administrators should implement network segmentation to limit access to router management interfaces and employ network access control measures to prevent unauthorized access. Additionally, regular security audits should verify that no plaintext credentials are stored or transmitted within web applications, and organizations should implement monitoring solutions to detect unusual access patterns to router management interfaces. The vulnerability demonstrates the critical importance of secure coding practices and input validation, particularly in web applications that handle sensitive authentication data, as outlined in OWASP Top Ten category A03:2021 - Injection and A07:2021 - Identification and Authentication Failures.