CVE-2026-88014

### Summary `backend/archive` mounts a zip file as a browsable, syncable rclone `Fs` (e.g. `rclone lsf :zip:downloaded.zip` or `rclone copy :zip:downloaded.zip dest:`). Go's `archive/zip` package does not sanitize `file.Name` - it is taken verbatim from the untrusted zip's central directory. `readZip()` in `backend/archive/zip/zip.go` applies `path.Clean` to the entry name, but this alone cannot fully neutralize a name with more `..` components than real segments preceding them (e.g. `"../../etc/cron.d/evil"` stays exactly as-is after cleaning). When the archive is mounted with an empty root (the common case), there was no check at all that the resulting name stayed inside the archive's own namespace, so it was stored verbatim and returned unchanged by `Object.Remote()`. `fs/sync`/`fs/operations` use `srcObj.Remote()` directly as the destination-relative path when copying between filesystems, so a maliciously crafted zip file can cause `rclone copy`/`sync` to attempt writes outside the intended destination directory on whatever backend it targets - this is the well-known "Zip Slip" vulnerability class (https://security.snyk.io/research/zip-slip-vulnerability) applied to rclone's own zip-mounting backend. It is distinct from `cmd/archive/extract`, which already validates via its own `destPath()` choke point and is not affected. ### Details Vulnerable code (before fix), `backend/archive/zip/zip.go`, `(*Fs).readZip`: ```go for _, file := range zr.File { remote := strings.Trim(path.Clean(file.Name), "/") if remote == "." { remote = "" } remote = path.Join(f.prefix, remote) if f.root != "" { // Ignore all files outside the root if !strings.HasPrefix(remote, f.root) { continue } ... } ... o := &Object{f: f, remote: remote, ...} dt.Add(o) } ``` The escape check only ran when `f.root != ""`, and even then used a bare `strings.HasPrefix` with no boundary check (so `f.root="foo"` incorrectly also matched a sibling entry `"foobar"`). ### PoC Built a zip in mem