CVE-2021-20155 in AC2600 TEW-827DRU
Summary
by MITRE • 12/31/2021
Trendnet AC2600 TEW-827DRU version 2.08B01 makes use of hardcoded credentials. It is possible to backup and restore device configurations via the management web interface. These devices are encrypted using a hardcoded password of "12345678".
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Analysis
by VulDB Data Team • 01/05/2022
The vulnerability identified as CVE-2021-20155 affects Trendnet AC2600 TEW-827DRU routers running firmware version 2.08B01 and represents a critical security weakness stemming from the improper handling of authentication credentials. This issue manifests through the device's configuration backup and restore functionality, which employs a hardcoded password that remains unchanged across all affected units. The flaw directly violates security best practices and creates an exploitable condition that allows unauthorized access to sensitive network configurations.
The technical implementation of this vulnerability involves the use of a hardcoded cryptographic key within the device's firmware, specifically a static password of "12345678" that serves as the encryption mechanism for configuration backups. This hardcoded credential approach creates a persistent security risk because the password is embedded within the device software and cannot be modified by administrators. The vulnerability resides in the device's web-based management interface, where users can initiate backup operations that automatically encrypt configuration data using this predetermined password. This design pattern represents a fundamental flaw in the device's security architecture and aligns with CWE-798, which categorizes the use of hard-coded credentials as a severe weakness in software systems.
The operational impact of this vulnerability extends beyond simple unauthorized access to encompass potential network compromise and data exfiltration. An attacker who discovers this hardcoded credential can restore backup configurations without authentication, potentially gaining access to network settings, user credentials, and other sensitive information stored within the router's configuration. This capability enables adversaries to manipulate network parameters, establish persistent access points, or extract valuable information that could be used for further attacks within the network infrastructure. The vulnerability creates a direct pathway for lateral movement and privilege escalation, particularly in environments where the router serves as a central network component.
The security implications of this vulnerability are compounded by the fact that it affects a widely deployed consumer-grade router model, making it a prime target for automated exploitation campaigns. The hardcoded nature of the password means that all devices running the affected firmware version are equally vulnerable, creating a massive attack surface that can be exploited at scale. Network defenders must consider that this vulnerability provides attackers with the ability to maintain persistence on compromised networks through configuration restoration operations, potentially allowing for long-term access without detection. This weakness also enables attackers to bypass traditional authentication mechanisms and gain access to network management interfaces that would otherwise require proper credentials.
Mitigation strategies for CVE-2021-20155 should focus on immediate firmware updates from Trendnet, as the manufacturer has likely released patches addressing this issue. Organizations should also implement network segmentation to limit the impact of potential exploitation, disable unnecessary backup and restore functionality when not required, and monitor network traffic for signs of unauthorized configuration changes. The vulnerability demonstrates the critical importance of proper credential management and the dangers of embedded hardcoded values in network infrastructure devices, aligning with ATT&CK technique T1566 for credential access and T1071 for application layer protocol usage. Administrators should also consider implementing network monitoring solutions that can detect unusual backup and restore activities that might indicate exploitation attempts.