Contao is an Open Source CMS. From version 5.7.0 until 5.7.12, TableAccessVoter::hasAccessToModule() in core-bundle/src/Security/Voter/DataContainer/TableAccessVoter.php caches authorization decisions using only $tokenHash, a hash of the user's security token, and omits the table returned by getDataSource(). If one request first checks a table allowed to the user and then a different denied table, the voter can reuse the allowed result, while DefaultDataContainerVoter can convert an incorrect abstention into a grant. A low-privileged backend user can consequently read, create, update, or delete records in tables outside assigned module permissions, including tables containing member or newsletter-subscriber data. This issue is fixed in version 5.7.12.

Affected: Packagist: contao/core-bundle

Due to a caching defect in the security voter that governs table-level access to Contao's Data Container (DCA) backend, a low-privileged, non-admin backend user can obtain unauthorized read, create, update, and delete access to database tables outside their assigned module permissions. This includes tables containing sensitive personal data, such as frontend member records and newsletter subscriber e-mail addresses.

### Vulnerability Details

In plain terms: Contao's backend is organized into modules (e.g. "News", "Members"). Every backend user is assigned to a group, and that group decides which modules, and therefore which database tables, they are allowed to work with. Before Contao lets a user touch a table, it is supposed to check: "does this user's group actually include this table?"

To avoid doing that check over and over, Contao remembers the answer for the rest of the request. The problem is that it remembers the answer under the wrong label. Instead of remembering "is this user allowed to access table X", it only remembers "is this user allowed to access something", without recording which table the answer was actually about. So if a request first checks a table the user IS allowed to see, and then checks a second, completely different table the user is NOT allowed to see, Contao reuses the first answer for the second table too. The user ends up with access to a table their group was never given permission for. ### Technical detail Contao's backend enforces…