CVE-2026-50283

We have identified an authorization issue in Craft CMS `AssetsController::actionReplaceFile` that can delete a source asset without source delete permission by supplying both `assetId` and `sourceAssetId`. ### Description Craft CMS’s `craft\\controllers\\AssetsController::actionReplaceFile()` supports replacing a target asset file using another existing asset as the source. The action loads: - `$assetToReplace` from `assetId` - `$sourceAsset` from `sourceAssetId` It then enforces replace permissions using `($assetToReplace ?: $sourceAsset)`. When both IDs are provided, this expression resolves to the target asset so no permission check is performed against the source asset volume. ```php $this->requireVolumePermissionByAsset('replaceFiles', $assetToReplace ?: $sourceAsset); $this->requirePeerVolumePermissionByAsset('replacePeerFiles', $assetToReplace ?: $sourceAsset); ``` [*src/controllers/AssetsController.php:L433-L434*](https://github.com/craftcms/cms/blob/5.x/src/controllers/AssetsController.php#L433-L434) In the branch where both assets are present, Craft copies the source file into the target and then deletes the source asset. There is no check for `deleteAssets:<sourceVolumeUid>` or `deletePeerAssets:<sourceVolumeUid>` for the source asset before deletion. ```php $assets->replaceAssetFile($assetToReplace, $tempPath, $assetToReplace->getFilename(), $sourceAsset->getMimeType()); Craft::$app->getElements()->deleteElement($sourceAsset); ``` [*src/controllers/AssetsController.php:L462-L463*](https://github.com/craftcms/cms/blob/5.x/src/controllers/AssetsController.php#L462-L463) ### Impact An authenticated user who can replace files in one volume can delete assets in another volume where they do not have delete permission, as long as they can obtain a `sourceAssetId`. This can lead to unauthorized asset deletion, broken content references, and data loss.