---
id: CVE-2026-107850
title: Contao is an Open Source CMS
summary: >-
  Contao is an Open Source CMS. From version 5.7.1 until 5.7.12,
  core-bundle/config/services.yaml registers the preview access voter as
  Contao\CoreBundle\Security\Voter\DataContainer\PreviewAccessVoter although the
  shipped class is Preview…
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N'
cwe:
  - CWE-639
  - CWE-862
vendor: contao
product: contao/core-bundle
affected:
  - 'contao/core-bundle >= 5.7.1, < 5.7.12'
patched:
  - contao/core-bundle 5.7.12
published: '2026-10-09'
updated: '2026-10-09'
sourceUpdated: '2026-10-09T21:17:02.770'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-107850'
references:
  - url: >-
      https://github.com/contao/contao/commit/6b483d380a4b2dc61432c4c697e411508f93bf91
    label: security-advisories@github.com
  - url: 'https://github.com/contao/contao/releases/tag/5.7.12'
    label: security-advisories@github.com
  - url: 'https://github.com/contao/contao/security/advisories/GHSA-q6wp-fr43-gm9v'
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-q6wp-fr43-gm9v'
tags:
  - nvd
  - ghsa
  - composer
aliases:
  - GHSA-q6wp-fr43-gm9v
ecosystem: composer
ingestedAt: '2026-10-09T21:12:42.325Z'
---

## Overview

Contao is an Open Source CMS. From version 5.7.1 until 5.7.12, core-bundle/config/services.yaml registers the preview access voter as Contao\CoreBundle\Security\Voter\DataContainer\PreviewAccessVoter although the shipped class is PreviewVoter. Symfony therefore omits voter autoconfiguration and removes the private service, so PreviewVoter::hasAccess() never enforces ownership. A non-admin backend user with the preview_link module can list every tl_preview_link record, obtain signed share URLs created by other users, and use them to view unpublished pages with showUnpublished despite lacking page permission. The advisory does not establish editing or deletion of foreign links. This issue is fixed in version 5.7.12.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-107850)

Affected packages:

- `contao/core-bundle >= 5.7.1, < 5.7.12`

Patched in:

- `contao/core-bundle 5.7.12`

Source: https://github.com/advisories/GHSA-q6wp-fr43-gm9v