vulnerability / NVI-00004163 / Revision 2
Contao: Improper access control in the preview links module
OSV carries this publisher advisory for contao/core-bundle. This is an aggregated source copy; consult the original publisher and compare update dates.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
4.3 MEDIUM (3.1)
security-advisories@github.com severity; no combined Null risk score.
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
contao/core-bundle
source listedECOSYSTEM: introduced 5.7.1; fixed 5.7.12
`core-bundle/config/services.yaml` registers the preview access voter with the class `Contao\CoreBundle\Security\Voter\DataContainer\PreviewAccessVoter`, but the class shipped on disk is named `PreviewVoter`. Symfony resolves the class with `getReflectionClass($class, false)`, gets `null`, silently skips the interface based autoconfiguration that would have tagged it as a voter, and the now untagged private service is removed when the container is compiled. The application boots without a warning, and the ownership rule in `PreviewVoter::hasAccess()` is never executed. `tl_preview_link` has no compensating SQL filter on `createdBy`, so any non administrator back end user whose group holds the `preview_link` module reads every preview link on the installation and lifts the already signed share URLs straight out of the list. Following one grants front end preview of the target page, with `showUnpublished` and with no page permission check, to anyone at all. ### Impact A non administrator back end user reads every preview link on the installation, including links created by administrators, and lifts the already signed share URLs out of the list. Following one grants front end previe
03 / Response
What to do next
- vendor patch
The original advisory lists fixed boundaries 5.7.12 for contao/core-bundle. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. NIST National Vulnerability Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
- NVD lastModified does not establish freshness of every associated CPE record.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-q6wp-fr43-gm9v ↗
GitHub Advisory Database via OSV · vendor advisory
Observed . GitHub-origin advisory, CC-BY-4.0; OSV is an aggregate copy, not independent corroboration.
- CVE-2026-107850 ↗
NIST National Vulnerability Database · official catalog
Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 2 ·
Source facts changed; compare the preserved prior revision.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.