Rclone, a popular command‑line tool for synchronizing files with cloud storage, has a critical flaw in its Remote Control (RC) interface. The operations/fsinfo endpoint is mistakenly exposed without authentication, allowing an attacker to submit a payload that specifies an arbitrary backend. The rc.GetFs function can create any backend on demand, and for the WebDAV backend the bearer_token_command is run during initialization. Consequently, a single unauthenticated request can trigger local command execution on the host that runs Rclone, exploiting weaknesses in improper access control (CWE‑306), OS command injection (CWE‑78), and unsafe code execution (CWE‑94). The vulnerability exists in Rclone versions 1.48.0 through 1.73.4, and is fixed in 1.73.5.

Affected systems are installations of Rclone 1.48.0 up to, but not including, 1.73.5. The vulnerability is relevant to any deployment that exposes the RC endpoint without global HTTP authentication, whether running as a standalone binary or within a container or scripted environment. Attackers could reach a vulnerable instance over the network and issue the operations/fsinfo request with crafted backend parameters.

The CVSS score of 9.2 classifies this flaw as critical, and the EPSS score of 10% indicates it is likely to be attempted by adversaries. Because the endpoint accepts unauthenticated requests, the attack vector is remote network access; no credentials or privileged permissions are required. While the vulnerability is not currently listed in CISA’s KEV catalog, the combination of high severity and moderate exploitation potential warrants urgent attention.