Affected: Bitnami: rclone

rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.64.0 until 1.75.1, the FTP auth-proxy driver in cmd/serve/ftp/ftp.go stores one obscured password per username in the server-wide userPass map[string]string instead of binding the credential or VFS to the authenticated session. If two accepted credentials use the same username but resolve to different proxy backends, a later CheckPasswd login overwrites userPass[user], and subsequent getVFS operations on the first session are reauthorized with the later password. The first session can then read, create, overwrite, rename, or delete objects using the second credential’s backend authority. Exploitation requires the later same-username login to occur while the first session remains open. This issue is fixed in version 1.75.1.

rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.64.0 until 1.75.1, the FTP auth-proxy driver in cmd/serve/ftp/ftp.go stores one obscured password per username in the server-wide userPass map[string]string instead of binding the credential or VFS to the authenticated session. If two accepted credentials use the same username but resolve to different proxy backends, a later CheckPasswd login overwrites userPass[user], and subsequent getVFS operations on the first session are reauthorized with the later password. The first session can then read, create, overwrite, rename, or delete objects using the second credential’s backend authority. Exploitation requires the later same-username login to occur while the first session remains open. This issue is fixed in version 1.75.1.

Affected: Go: github.com/rclone/rclone

## Summary

The FTP auth-proxy driver stores one obscured password per username in a server-wide map. It does not bind the credential or returned VFS to the authenticated FTP session. If two accepted credentials use the same username but resolve to different proxy backends, the later login overwrites the map entry. Subsequent operations on the first, still-authenticated session are re-authorized with the later session's password and execute against the later session's backend.

This is not exploitable in every auth-proxy deployment. It requires a proxy that accepts distinct credentials for the same username and returns different roots or backend configurations, plus a later login while the attacker's session remains open. The behavior is nevertheless within the supported model: `cmd/serve/proxy` keys VFS entries by username, authentication material, and client IP specifically so a new credential can produce a fresh backend.

Confirmed affected versions are `v1.75.0` and development commit `5629f2668c69149bf3d9d8e2a25bb32a2648606e`. The username-global map was introduced in `v1.64.0`, but versions before credential-aware proxy caching may require cache expiration or different timing and are not claimed as confirmed here.

## Affected Assets & Attack Surface

- `cmd/serve/ftp/ftp.go:170-178` defines `userPass map[string]string` as driver-global state keyed only by username. - `cmd/serve/ftp/ftp.go:318-335` validates `(user, pass)` through the proxy and then overwrites `d.userP…

Withdrawn by the publisher.

Affected: Ubuntu:18.04:LTS: rclone, Ubuntu:Pro:20.04:LTS: rclone, Ubuntu:Pro:22.04:LTS: rclone, Ubuntu:Pro:24.04:LTS: rclone, Ubuntu:Pro:26.04:LTS: rclone

rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.64.0 until 1.75.1, the FTP auth-proxy driver in cmd/serve/ftp/ftp.go stores one obscured password per username in the server-wide userPass map[string]string instead of binding the credential or VFS to the authenticated session. If two accepted credentials use the same username but resolve to different proxy backends, a later CheckPasswd login overwrites userPass[user], and subsequent getVFS operations on the first session are reauthorized with the later password. The first session can then read, create, overwrite, rename, or delete objects using the second credential’s backend authority. Exploitation requires the later same-username login to occur while the first session remains open. This issue is fixed in version 1.75.1.