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[ CVE-2026-107850 · Published 9 Oct 2026 ]

Contao: Improper access control in the preview links module

CVSS 4.3 EPSS <1%Fix available

[ Description ]Official description

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module can list every tl_preview_link record, obtain signed share URLs created by other users, and use them to view unpublished pages with showUnpublished despite lacking page permission.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.

[ Fixes ]Fixes and patches

  • contao/core-bundle 5.7.12Fixed version · GitHub Advisories · composer package contao/core-bundle: upgrade to 5.7.12 or later (affected >= 5.7.1, < 5.7.12)

[ Packages ]Affected open-source packages

  • contao/core-bundle composerAffected >= 5.7.1, < 5.7.12 · fixed in 5.7.12 · GHSA-q6wp-fr43-gm9v

[ References ]References