CVE-2020-14078 in TEW-827DRU
Summary
by MITRE
TRENDnet TEW-827DRU devices through 2.06B04 contain a stack-based buffer overflow in the ssi binary. The overflow allows an authenticated user to execute arbitrary code by POSTing to apply.cgi via the action wifi_captive_portal_login with a sufficiently long REMOTE_ADDR key.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 06/15/2020
The TRENDnet TEW-827DRU wireless router firmware version 2.06B04 contains a critical stack-based buffer overflow vulnerability in the ssi binary component. This vulnerability represents a significant security flaw that can be exploited by authenticated attackers to gain arbitrary code execution on the affected device. The vulnerability specifically manifests when processing HTTP POST requests to the apply.cgi endpoint with the action parameter set to wifi_captive_portal_login. The flaw occurs due to inadequate input validation of the REMOTE_ADDR HTTP header field, which is directly used in a vulnerable buffer operation without proper bounds checking. This type of vulnerability falls under the Common Weakness Enumeration category CWE-121, which describes stack-based buffer overflow conditions where insufficient boundary checks allow attackers to overwrite adjacent memory locations on the program stack.
The operational impact of this vulnerability extends beyond simple code execution as it provides attackers with complete control over the affected router. Once exploited, an attacker can manipulate network configurations, intercept traffic, redirect users to malicious sites, or establish persistent backdoors within the network infrastructure. The vulnerability requires only authenticated access to the device's web interface, which is often easily obtained through default credentials or weak authentication mechanisms commonly found in consumer-grade networking equipment. This makes the attack surface particularly concerning for enterprise environments where such devices may be deployed without proper security hardening. The attack vector specifically targets the captive portal login functionality, which is typically used for guest network access control and authentication services, making it a prime target for exploitation.
Security professionals should recognize this vulnerability as part of the broader ATT&CK framework's privilege escalation and execution techniques, particularly within the context of router and network device exploitation. The vulnerability demonstrates the critical importance of input validation and proper memory management in embedded systems, especially those handling network traffic and authentication processes. Organizations should implement immediate mitigations including firmware updates from TRENDnet, network segmentation to limit access to affected devices, and monitoring for suspicious authentication patterns or network traffic anomalies. The vulnerability also highlights the need for regular security assessments of network infrastructure components and the implementation of secure coding practices in embedded firmware development. Additionally, network administrators should consider disabling unnecessary services and features, particularly captive portal functionality, when not required for operations. The remediation process should involve thorough testing of firmware updates to ensure compatibility and prevent service disruption while addressing the underlying buffer overflow condition that enables arbitrary code execution.