CVE-2026-49980: Rclone: Unauthenticated command execution in `rclone rcd --rc-serve` via inline remote instantiation, bypassing CVE-2026-41179 fix

rclone rcd --rc-serve accepts unauthenticated GET and HEAD requests to paths of the form:

/[remote:path]/object

The remote value is parsed from the URL and passed to normal backend initialization. Inline remote configuration can set backend options that execute local commands during initialization. As a result, a single unauthenticated GET or HEAD request can execute a command as the rclone process user.

Versions from 1.55.0 onwards are vulnerable to command execution. Earlier versions (from 1.46.0) are vulnerable to the unauthenticated local file read described under “Additional impact” but not to command execution, because inline backend option overrides did not exist until 1.55.0.