Craft CMS vulnerable to Server-Side Request Forgery (SSRF) via GraphQL Asset Upload Mutation

Craft is a platform for creating digital experiences. In versions 5.0.0-RC1 through 5.8.20 and 4.0.0-RC1 through 4.16.16, the Craft CMS GraphQL `save_<VolumeName>_Asset` mutation is vulnerable to Server-Side Request Forgery (SSRF). This vulnerability arises because the `_file` input, specifically its `url` parameter, allows the server to fetch content from arbitrary remote locations without proper validation. Attackers can exploit this by providing internal IP addresses or cloud metadata endpoints as the `url`, forcing the server to make requests to these restricted services. The fetched content is then saved as an asset, which can subsequently be accessed and exfiltrated, leading to potential data exposure and infrastructure compromise. This exploitation requires specific GraphQL permissions for asset management within the targeted volume. Users should update to the patched 5.8.21 and 4.16.17 releases to mitigate the issue.