CVE-2026-107850 Contao: Improper access control in the preview links module
Non-admin users can view unpublished pages and other users' preview links due to improper access control in the preview module.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-107850?
CVE-2026-107850 is a medium-severity missing authorization vulnerability in contao, published on 9 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
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module can list every tl_preview_link record, obtain signed share URLs created by other users, and use them to view unpublished pages with showUnpublished despite lacking page permission.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.
Which versions are affected by CVE-2026-107850?
2 open source packages ship an affected version, including contao/core-bundle.
| Package | Affected | Fixed in |
|---|---|---|
contao/core-bundle Packagist | From 5.7.1 | 5.7.12 |
contao/core-bundle Packagist | From 5.7.1 | 5.7.12 |
How do I fix CVE-2026-107850?
Upgrade contao/core-bundle to 5.7.12 or later.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-107850 being exploited?
There is no known exploitation of CVE-2026-107850 in the wild and no public exploit code.
Sources
Also known as GHSA-q6wp-fr43-gm9v.