Contao up to 5.7.11 Preview Access Voter services.yaml PreviewVoter::hasAccess permission

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Contao up to 5.7.11. This affects the function PreviewVoter::hasAccess of the file core-bundle/config/services.yaml of the component Preview Access Voter. This manipulation causes permission. This vulnerability is handled as CVE-2026-107850. The attack can be initiated remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Contao up to 5.7.11 and classified as problematic. Affected by this vulnerability is the function PreviewVoter::hasAccess of the file core-bundle/config/services.yaml of the component Preview Access Voter. The manipulation with an unknown input leads to a permission vulnerability. The CWE definition for the vulnerability is CWE-275. As an impact it is known to affect confidentiality. The summary by CVE is:

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module can list every tl_preview_link record, obtain signed share URLs created by other users, and use them to view unpublished pages with showUnpublished despite lacking page permission.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

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-107850 since 10/09/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1222 according to MITRE ATT&CK.

Upgrading to version 5.7.12 eliminates this vulnerability.

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Productinfo

Name

• Contao

Version

• 5.7.0
• 5.7.1
• 5.7.2
• 5.7.3
• 5.7.4
• 5.7.5
• 5.7.6
• 5.7.7
• 5.7.8
• 5.7.9
• 5.7.10
• 5.7.11

Website

• Product: https://github.com/contao/contao/

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