Craft CMS is a content management system (CMS). From 5.0.0-RC1 to before 5.9.18, 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 vulnerability is fixed in 5.9.18.

Affected: Packagist: craftcms/cms

## Summary

`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.

## Details

The vulnerability is in `src/controllers/AssetsController.php` at line 1437. The method:

1. Calls `requireCpRequest()` — verifies the request targets the CP, enforces `accessCp` permission via `Controller::_enforceAllowAnonymous()`, but does NOT enforce any volume-level permission. 2. Fetches any asset by ID with `Asset::findOne($assetId)` — no `editable`/`savable` scope filter, so all assets across all volumes are reachable. 3. Returns sensitive structural data via JSON.

## Impact

- Any authenticated control panel user with only `accessCp` permissi…