gonic is a music streaming server / free-software subsonic server API implementation. Prior to version 0.21.0, the Subsonic API endpoints `/rest/deletePlaylist.view` and `/rest/getPlaylist.view` perform no per-resource authorization. Once authenticated as any user (admin or not), an attacker can delete any playlist owned by any other user (including admin) by passing its `id` and read the full contents (name, comment, song list) of any other user's **private** (non-public) playlist by passing its `id`. The Subsonic playlist `id` is `base64url("<userID>/<filename>.m3u")`. Because filenames are user-supplied or time-derived and the `userID` is a small integer, IDs are guessable and frequently exposed (e.g. a previously-public playlist that was later made private still has the same ID). This breaks the multi-user trust boundary of gonic: a low-privileged user can wipe an administrator's curated playlists, and a user can exfiltrate any private playlist they obtain an ID for. The issue was fixed in commit `6dd71e6a3c966867ef8c900d359a7df75789f410`, which is part of version 0.21.0.

gonic is a music streaming server / free-software subsonic server API implementation. The maintainer's fix in commit `6dd71e6a3c966867ef8c900d359a7df75789f410` added an ownership check based on `playlist.UserID`. However, `playlist.UserID` is derived from the first path segment of the attacker-controlled playlist ID, with no path containment on the resolved file path. Any authenticated Subsonic user can therefore bypass the ownership check and read any other user's playlist, delete any other user's playlist, and probe arbitrary file paths on the host for existence/readability. This is a bypass of the boundary the `6dd71e6` fix is trying to enforce; it is closely related to the original GONIC-1 IDOR but uses a different primitive (path traversal in the `id` parameter rather than direct cross-user access). Commit 0824bed88f6bbc490ba28bf09d28e5dfeb07b445 in version 0.21.0 fixes the issue.

gonic is a music streaming server / free-software subsonic server API implementation. Prior to version 0.21.0, a logic error in `ServeCreateOrUpdatePlaylist` allows any authenticated Subsonic user (including non-admin) to write playlist M3U content to an attacker-controlled absolute filesystem path on the gonic host, and to create intermediate directories with `0o777` permissions. The bug is independent of CVE-2026-49338 and CVE-2026-49339. It is an unreachable guard clause combined with no path containment in `Store.Write`. Version 0.21.0 patches the issue.