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Findings

CVE-2026-107848

Contao: Cross-site request forgery in custom backend actions

Published Oct 9, 2026 · updated Oct 9, 2026

is the only generic validator in Contao and it only runs on POST. On the GET side the guard is local and declarative, and it only fires when an parameter is present. Every back end action dispatched through a different parameter therefore has no CSRF protection at all. This is a family rather than a single bug. ### Impact An attacker who gets a logged in back end user to load a URL performs back end actions as that user, with no token and no confirmation. Because the exposure follows from the dispatch mechanism rather than from one callback, every present and future action inherits it. **Honest bound.** The victim must be authenticated in the back end and must load the URL, and the reachable actions are limited to the modules that user can access. We have not found a action that grants privileges; the ones we verified are destructive or state changing rather than escalating.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 9, 2026 · Catalog

    Detected

    is the only generic validator in Contao and it only runs on POST. On the GET side the guard is local and declarative, and it only fires when an parameter is present. Every back end action dispatched through a different parameter therefore has no CSRF protection at all. This is a family rather than a single bug. ### Impact An attacker who gets a logged in back end user to load a URL performs back e

  2. Oct 9, 2026 · Catalog

    Fix available

    Packagist contao/core-bundle 4.0.0 → 5.3.50

  3. Oct 9, 2026 · Catalog

    Fix available

    Packagist contao/core-bundle 5.4.0-RC1 → 5.7.12

  4. Oct 9, 2026 · GitHub Advisory Database

    Fix available

    contao/core-bundle fixed in 5.3.50; contao/core-bundle fixed in 5.7.12

  5. Oct 9, 2026 · GitHub Advisory Database

    Fix available

    contao/core-bundle fixed in 5.3.50

  6. Oct 9, 2026 · GitHub Advisory Database

    Fix available

    contao/core-bundle fixed in 5.7.12

  7. Oct 9, 2026 · Catalog

    Updated

    is the only generic validator in Contao and it only runs on POST. On the GET side the guard is local and declarative, and it only fires when an parameter is present. Every back end action dispatched through a different parameter therefore has no CSRF protection at all. This is a family rather than a single bug. ### Impact An attacker who gets a logged in back end user to load a URL performs back e

Affected

  • Packagist contao/core-bundle4.0.0 → 5.3.50
  • Packagist contao/core-bundle5.4.0-RC1 → 5.7.12

Sources

References