CVE-2026-44012: Craft CMS's Missing Volume Permission Check in AssetsController::actionShowInFolder Allows Information Disclosure

AssetsController::actionShowInFolder() fetches an asset by ID and returns its filename and complete folder hierarchy (including volume handle, volume UID, folder names, folder UIDs, and folder URI paths) without checking whether the requesting user has viewAssets or viewPeerAssets permission on the asset’s volume. Any authenticated CP user — even one with zero volume permissions — can enumerate asset filenames and the full folder structure of any volume by supplying arbitrary asset IDs.

This follows the exact same incomplete-patch pattern as four GHSAs merged on 2026-02-25 (GHSA-x76w-8c62-48mg, GHSA-vgjg-248p-rfm2, GHSA-5pgf-h923-m958, GHSA-3pvf-vxrv-hh9c), all of which added requireVolumePermissionByAsset() + requirePeerVolumePermissionByAsset() to sibling AssetsController actions. The actionShowInFolder method was introduced thirteen days before the patch wave and was not included in it.