Vulnerabilities

rclone's `serve s3` command, when configured with an --auth-proxy but without --auth-key, registers any client-chosen access key ID with an empty secret and passes that identifier to the proxy without an independent per-identity credential. An unauthenticated network attacker can send an S3 request signed via SigV4 with an arbitrary access key ID and an empty secret; because both authPairMiddleware and gofakes3 validate against that same empty secret, the signature verifies and the request is accepted. The attacker then reaches whatever backend the auth-proxy script resolves for the chosen identity, with high impact on confidentiality, integrity and availability (CVSS 9.8). Only deployments running rclone prior to 1.75.1 with `serve s3`, --auth-proxy enabled and no --auth-key are affected; other rclone configurations are not implicated. No public proof-of-concept is known and the issue is not in the CISA KEV catalog, so no confirmed exploitation has been reported.

Do: Upgrade to rclone 1.75.1 or later. If upgrading is not immediately possible, set --auth-key on `serve s3` deployments that use --auth-proxy, or restrict network access to the S3 endpoint to trusted clients. Check serve s3 access logs for successful requests using unexpected or arbitrary access key IDs, which would indicate exploitation attempts.

Rclone is a command-line program to sync files and directories to and from different cloud storage providers. Prior to 1.74.4, rclone serve restic --private-repos enforces authorization using the routed user path segment while building the backend object key from the raw uncleaned URL path, allowing an authenticated user to include .. in a request such as //..//config and read, overwrite, or delete another user's private repository on backends that clean path components. This issue is fixed in version 1.74.4.

Rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.46.0 until 1.74.3, 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. This vulnerability is fixed in 1.74.3.