CVE-2026-71415

### TL;DR This vulnerability affects all Kirby sites where users of a particular role have access to the REST API (`access.panel` permission is enabled) but no permission to upload any kind of file (`files.create`, `files.replace` and `user/users.update` permissions are all disabled). It was possible to fill up the temporary directory for chunked uploads with unfinished chunks even as a user without any upload permission. **This vulnerability is of high severity for affected sites.** Your Kirby sites are *not* affected if you intend all users of your site to be able to upload files. The vulnerability can only be exploited by authenticated users. It was *not* possible to bypass the actual permission checks for any files that end up in the `content` or `site/accounts` folders. ---- ### Introduction Missing authorization allows authenticated users to perform actions they are not intended to have access to. The effects of missing authorization can include unauthorized access to sensitive information as well as unauthorized changes to content or system information. ### Affected components Kirby's REST API provides routes to upload files, specifically to create content files, replace existing content files and to create and replace user avatars. Each upload route takes either full file upload requests or chunked upload requests that can be continued in subsequent requests. During a chunked upload, the incomplete state of the uploaded file is stored in a temporary directory until the last chunk completes the file. At this time, the final permission and business logic checks are performed before the complete file is moved to its final destination. ### Impact In affected releases, the chunk upload handler did not check for the user's file upload permissions before storing incomplete chunk data in the temporary directory. This allowed attackers without upload permissions to upload multiple large files in chunks. If the final chunk was never provided, Kirby would