Craft CMS up to 4.17.13/5.9.20 actionReplaceFile assetToReplace authorization

Summaryinfo

A vulnerability labeled as problematic has been found in Craft CMS up to 4.17.13/5.9.20. This affects the function AssetsController::actionReplaceFile. Executing a manipulation of the argument assetToReplace can lead to authorization. The identification of this vulnerability is CVE-2026-50283. The attack may be launched remotely. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Craft CMS up to 4.17.13/5.9.20. It has been declared as problematic. This vulnerability affects the function AssetsController::actionReplaceFile. The manipulation of the argument assetToReplace with an unknown input leads to a authorization vulnerability. The CWE definition for the vulnerability is CWE-862. The product does not perform an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect integrity, and availability. CVE summarizes:

Craft CMS is a content management system (CMS). Versions 5.0.0-RC1 through 5.9.20, and 4.0.0-RC1 through 4.17.13 contain an authorization issue in the AssetsController::actionReplaceFile that can delete a source asset without source delete permission by supplying both assetId and sourceAssetId. AssetsController::actionReplaceFile() supports replacing a target asset file using another existing asset as the source. The action loads: assetId -> $assetToReplace and sourceAssetId -> $sourceAsset, then enforces replace permissions using ($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. When both assets are present, Craft copies the source file into the target and then deletes the source asset. There is no deletion check for for the source asset. 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, leading to broken content references and data loss. This issue has been fixed in versions 4.17.14 and 5.9.21.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-50283 since 06/04/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available.

Upgrading to version 4.17.14 or 5.9.21 eliminates this vulnerability. Applying the patch 2c2579c7f1030872423f268d0c8b48377101961d is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Content Management System

Vendor

• Craft

Name

• CMS

Version

• 4.17.0
• 4.17.1
• 4.17.2
• 4.17.3
• 4.17.4
• 4.17.5
• 4.17.6
• 4.17.7
• 4.17.8
• 4.17.9
• 4.17.10
• 4.17.11
• 4.17.12
• 4.17.13
• 5.9.0
• 5.9.1
• 5.9.2
• 5.9.3
• 5.9.4
• 5.9.5
• 5.9.6
• 5.9.7
• 5.9.8
• 5.9.9
• 5.9.10
• 5.9.11
• 5.9.12
• 5.9.13
• 5.9.14
• 5.9.15
• 5.9.16
• 5.9.17
• 5.9.18
• 5.9.19
• 5.9.20

License

• free

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