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.
Preconditions for this vulnerability are:
--rc flag or by running the rclone rcd server--rc-addr flag is in use--rc-user/--rc-pass/--rc-htpasswd/etc--rc-serve flag must be in useAn unauthenticated network attacker who can reach the RC HTTP listener can execute commands as the rclone process user.
Additional impact observed during testing:
GET and HEAD both trigger backend initialization.local remotes.global.* options can mutate process-wide rclone configuration, including global.http_proxy.<img> tag pointing at http://127.0.0.1:5572/.... This is an additional impact multiplier, not the primary attack precondition.--rc-user/--rc-pass
or --rc-htpasswd, which has always been the recommended deployment.--rc-serve if file serving is not needed.The vulnerabilities in this advisory have been fixed by two commits:
--rc-serve inline remotesglobal.* connection string options changing config{
"cwe_ids": [
"CWE-306",
"CWE-78"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-16T23:39:41Z",
"nvd_published_at": "2026-06-24T19:17:11Z",
"severity": "CRITICAL"
}