CVE-2026-88016

rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.70.0 until 1.75.1, the serve/start RC interface accepts per-server proxyOpt.AuthProxy settings, and the FTP and S3 constructors in cmd/serve/ftp/ftp.go and cmd/serve/s3/server.go incorrectly check the process-global proxy.Opt.AuthProxy value instead. When the global value is empty, the request-local authentication proxy is ignored: FTP falls back to the fixed filesystem with username anonymous and any password, while S3 with AuthKey serves the fixed RC fs rather than the backend selected by the proxy. The dedicated command-line servers that configure the global option are not affected. This issue is fixed in version 1.75.1.

rclone is a command-line program to sync files and directories to and from different cloud storage providers. Prior to 1.75.1, rclone serve s3 configured with --auth-proxy but without --auth-key allows authPairMiddleware to register any client-chosen accessKeyID with an empty ws.s3Secret. gofakes3 then verifies the request’s SigV4 signature against that same empty secret, while Server.auth passes the access key identifier as both the user and authentication value to the proxy without an independent per-identity secret. An unauthenticated network attacker can therefore choose an arbitrary access key, sign with an empty secret, and reach whatever backend the auth-proxy script resolves for that identity. This issue is fixed in version 1.75.1.

Rclone versions 1.46.0 through 1.74.2 have a vulnerability in server mode (rcd --rc-serve) that allows unauthenticated GET and HEAD requests to execute arbitrary system commands. An attacker can craft a URL containing remote storage configuration that executes local commands during initialization.

In Rclone from version 1.48.0 to 1.73.4, the RC endpoint `operations/fsinfo` is exposed without `AuthRequired: true` and accepts attacker-controlled `fs` input. An unauthenticated attacker can exploit this to execute arbitrary local commands on the server via the WebDAV backend, which runs `bearer_token_command` during initialization.

In Rclone, the RC endpoint `options/set` is exposed without `AuthRequired: true`, allowing modification of global runtime configuration. An unauthenticated attacker can set `rc.NoAuth=true`, disabling the authorization gate for many RC methods that normally require authentication, leading to unauthorized access to sensitive administrative functionality.

Rclone before v1.75.2 contains a credential exposure vulnerability in the b2 backend that leaks the live account Authorization token and SSE-C keys on HTTP redirects from --b2-download-url hosts. Attackers can observe a same-host HTTPS-to-HTTP downgrade redirect to capture the cleartext B2 token, or receive cross-host redirects disclosing SSE-C customer encryption keys.

Rclone before 1.75.2 contains a path traversal vulnerability in the local backend's translateLink function, which trims the .rclonelink suffix from a path after the containment check, so a name can resolve outside the destination root. Attackers can plant a directory named ...rclonelink in a source tree synced with --links and --metadata to change ownership, timestamps, and xattrs of the destination's parent directory.

Rclone from 1.52.0 before 1.75.2 contains a cross-site request forgery vulnerability in the pCloud backend's localhost OAuth callback, which disables the state check and trusts the hostname parameter. Malicious web pages can send a stateless request to port 53682 during authorization, planting attacker tokens and API hosts so later transfers reach the attacker.

Rclone from 1.64.0 before 1.75.2 contains an authentication bypass vulnerability in serve webdav that lets unauthenticated attackers skip authentication by sending OPTIONS requests. Attackers can probe arbitrary paths and compare Allow header values to determine whether files or collections exist, enabling namespace enumeration.

rclone from 1.37 before 1.74.2 contains a server-side request forgery vulnerability that allows unauthenticated attackers to redirect http and netstorage backend requests by supplying a double-slash root on an existing named remote via --rc-serve. Attackers can make HEAD/GET requests to attacker-chosen hosts to read responses, capture configured custom headers, or obtain valid NetStorage request signatures.