Tenda A21 Stack-Based Buffer Overflow Vulnerability in Wi-Fi Configuration Endpoint

A stack-based buffer overflow vulnerability has been identified in the Tenda A21 router, specifically in the firmware version 1.0.0.0. The issue arises in the Wi-Fi configuration function 'form_fast_setting_wifi_set' within the '/goform/fast_setting_wifi_set' file. The vulnerability allows remote attackers to manipulate the 'ssid' parameter, leading to potential arbitrary code execution with root privileges or causing a denial-of-service condition by crashing the device's management interface.

Impact

Exploitation of this vulnerability allows for remote code execution with root privileges or causes a denial-of-service condition by crashing the device's management interface, making it unavailable for user interactions.

Reproduction

The vulnerability can be reproduced by sending a crafted HTTP request to the '/goform/fast_setting_wifi_set' endpoint with an excessively long 'ssid' parameter. This can be done using a simple Python script that utilizes the 'requests' library to send the payload. The overflow can be verified by observing the crash of the 'httpd' process, which handles the web interface.

Remediation

Users are advised to update to a version of the firmware that addresses this vulnerability. If no such version is available, consider replacing the device with a more secure alternative.