CVE-2026-67204

Description

BookStack before 26.05.4 contains a broken access control vulnerability that allows authenticated API users with image-update or image-delete permissions to manipulate other users- avatars by exploiting missing content-type restrictions in the Image Gallery API endpoints. Attackers can supply a user avatar-s ID to the API controller, which loads any image type without the web controller-s gallery and drawio restrictions, and when the avatar-s uploaded_to field matches a page ID accessible to the attacker, the authorization check passes allowing the attacker to rename, replace, or delete the target user-s avatar without requiring user-management permission.