Auth bypass in Contao
CVE-2026-107850
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module can list every tl_preview_link record, obtain signed share URLs created by other users, and use them to view unpublished pages with showUnpublished despite lacking page permission.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.
Vulnerability class: IDOR (Insecure Direct Object Reference)
Published .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Contao — versions >= 5.7.1, < 5.7.12
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-107850?
- CVE-2026-107850 is a medium-severity vulnerability in Contao, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 4.3/10. Published 2026-10-09.
- How severe is CVE-2026-107850?
- Medium severity. CVSS v3 base score is 4.3 out of 10.