Vendredi 18 septembre 2026

Nextcloud Server

The Photos app's filter-based "smart albums" build their file listing using the search configuration (photosSourceFolders) of the user viewing the album, rather than the album owner's configuration. When an album owner shares a smart album with another user, that user's own folder configuration is used to determine which of the owner's files are searched — allowing them to discover files (name, file ID, and other metadata) in folders the album owner never intended to include in the shared album. This requires the album owner to have shared a filter-based smart album with the attacker; it does not allow access to arbitrary users' files without such a share.

Nextcloud Server

Circles' remote-instance signature verification fetches the attacker-supplied keyId URL before trust in the remote instance is established, and explicitly allows local/private addresses for this request, bypassing Nextcloud's core SSRF protections. The public, unauthenticated endpoints POST /apps/circles/event/ and POST /apps/circles/incoming/ reach this code path, allowing any unauthenticated user to force the server to issue a GET request to an internal address. The response body of the internal request is never returned to the requester, so this is blind SSRF: an attacker can determine whether an internal service is reachable, but cannot read its response contents through this endpoint alone.