Vikunja is an open-source self-hosted task management platform. Prior to version 2.2.1, TaskAttachment.ReadOne() queries attachments by ID only (WHERE id = ?), ignoring the task ID from the URL path. The permission check in CanRead() validates access to the task specified in the URL, but ReadOne() loads a different attachment that may belong to a task in another project. This allows any authenticated user to download or delete any attachment in the system by providing their own accessible task ID with a target attachment ID. Attachment IDs are sequential integers, making enumeration trivial. Version 2.2.1 patches the issue.
Exploitability
AV:NAC:LPR:LUI:NScope
S:UImpact
C:HI:HA:N8.1/CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:NOther