CVE-2021-20165 in AC2600 TEW-827DRU
Summary
by MITRE • 12/31/2021
Trendnet AC2600 TEW-827DRU version 2.08B01 does not properly implement csrf protections. Most pages lack proper usage of CSRF protections or mitigations. Additionally, pages that do make use of CSRF tokens are trivially bypassable as the server does not appear to validate them properly (i.e. re-using an old token or finding the token thru some other method is possible).
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Analysis
by VulDB Data Team • 01/05/2022
The vulnerability identified as CVE-2021-20165 affects Trendnet AC2600 TEW-827DRU wireless router running firmware version 2.08B01 and represents a critical cross-site request forgery weakness that fundamentally compromises the device's security posture. This issue stems from the absence of robust cross-site request forgery protection mechanisms across most administrative pages of the router's web interface, creating an environment where unauthorized users can potentially execute malicious actions on behalf of legitimate administrators. The vulnerability manifests as a complete failure to implement proper CSRF safeguards, leaving the device susceptible to attacks that could alter router configurations, modify network settings, or establish unauthorized access points without proper authentication.
The technical flaw lies in the router's web application implementation where CSRF tokens are either entirely absent from most pages or are implemented in a manner that provides no meaningful protection. When CSRF tokens are present, the system fails to properly validate them, allowing attackers to bypass authentication mechanisms through trivial methods such as token reuse or token extraction via side-channel attacks. This weakness directly corresponds to CWE-352, which defines cross-site request forgery as a vulnerability where the application fails to validate that requests originate from legitimate users. The implementation error creates a pathway for attackers to manipulate the router's configuration through forged requests, potentially leading to complete network compromise. The vulnerability's severity is amplified by the fact that it affects the administrative interface, which typically requires elevated privileges to access, making successful exploitation particularly dangerous.
The operational impact of this vulnerability extends beyond simple configuration changes, as it provides attackers with the ability to fundamentally alter network security settings and potentially gain persistent access to the local network. An attacker who successfully exploits this vulnerability could modify firewall rules, change administrator credentials, disable security features, or redirect network traffic through maliciously configured DNS settings. The implications are particularly severe for home and small office networks where router security is often overlooked, as compromised routers can serve as entry points for broader network infiltration. This vulnerability aligns with ATT&CK technique T1071.004, which describes the use of application layer protocols for command and control communications, as compromised routers can be used to establish persistent backdoors or facilitate lateral movement within networks. The vulnerability also maps to T1082, representing system information discovery, as attackers can potentially gather network topology information through router configuration modifications.
Mitigation strategies for this vulnerability require immediate firmware updates from Trendnet to address the CSRF implementation flaws and ensure proper token validation. Network administrators should implement additional security measures such as restricting administrative access to specific IP addresses, enabling two-factor authentication where available, and monitoring network traffic for suspicious patterns that might indicate exploitation attempts. The device should be configured to disable unnecessary services and features, particularly those that might expose administrative interfaces to untrusted networks. Organizations should also consider implementing network segmentation to limit the potential impact of router compromise and establish robust monitoring procedures to detect unauthorized configuration changes. The vulnerability underscores the importance of proper input validation and authentication mechanisms in network device firmware, as highlighted in industry standards such as the OWASP Top Ten and NIST cybersecurity guidelines for embedded systems. Given the nature of the vulnerability, it is essential to perform thorough network assessments and ensure that all network devices maintain current firmware versions to prevent exploitation of known vulnerabilities.