GHSA-7p4m-qxvv-g567: rclone: Local Encoding Path Traversal

Summary The local backend relies on its configurable filename encoder to prevent remote filename data from becoming operating-system path syntax. If a local destination uses an encoding that omits Dot, such as Slash, None, or Raw, a remote object's standard-encoded ．． component is decoded into an actual .. component. backend/local.localPath then passes the decoded name to filepath.Join, which resolves the component and produces a path outside the configured local root. An attacker who can create object names in a remote source that a victim copies or synchronizes to such a local destination can create or overwrite files outside the selected destination directory, with the permissions of the rclone process. The default local encoding includes Dot and is not affected by that exact path. This finding requires a non-default local encoding that preserves filesystem path syntax. On Windows, a second confirmed form uses a preserved backslash to turn a remote filename into a native ..\file path even when the destination encoding still includes Dot. This is not merely an odd filename-conversion result. The local remote's configured root is the destination selected by the user, and ordinary backend operations are expected to remain within it. Rclone documents custom and Raw encodings as filename-conversion controls; it does not document them as an opt-out from destination confinement. The defect is that confinement depends on an encoding mask instead of an independent post-conversion path check. Affected Assets & Attack Surface Confirmed affected versions - v1.51.0 through v1.74.4 - Local development commit tested: a0c09f1381ae93e2a9a33c529d170186c61ad058 - Public master inspected through commit c99b2d11edb0986cd2b1190e9fa25a58a3f12661 (2026-07-23) v1.51.0 introduced the configurable encoding option for the local backend. Encodings such as None or Slash could omit Dot from that version onward. The explicit Raw encoding was introduced later, in v1.68.0. Required desti