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.

$this->requireVolumePermissionByAsset('replaceFiles', $assetToReplace ?: $sourceAsset);
$this->requirePeerVolumePermissionByAsset('replacePeerFiles', $assetToReplace ?: $sourceAsset);

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.

$assets->replaceAssetFile($assetToReplace, $tempPath, $assetToReplace->getFilename(), $sourceAsset->getMimeType());
Craft::$app->getElements()->deleteElement($sourceAsset);

src/controllers/AssetsController.php:L462-L463

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.

Kodem intelligence

1. What is CVE-2026-50283? CVE-2026-50283 is a medium-severity security vulnerability in craftcms/cms (composer), affecting versions >= 5.0.0-RC1, < 5.9.21. It is fixed in 5.9.21, 4.17.14.
2. Which versions of craftcms/cms are affected by CVE-2026-50283? craftcms/cms (composer) versions >= 5.0.0-RC1, < 5.9.21 is affected.
3. Is there a fix for CVE-2026-50283? Yes. CVE-2026-50283 is fixed in 5.9.21, 4.17.14. Upgrade to this version or later.
4. Is CVE-2026-50283 exploitable, and should I be worried? Whether CVE-2026-50283 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2026-50283 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2026-50283?
   • Upgrade craftcms/cms to 5.9.21 or later
   • Upgrade craftcms/cms to 4.17.14 or later