CVE-2026-71311

Ein Angreifer kann mehrere Schwachstellen in rclone ausnutzen, um beliebigen Programmcode auszuführen, um einen Denial of Service Angriff durchzuführen, um Informationen offenzulegen, um Dateien zu manipulieren, und um Sicherheitsvorkehrungen zu umgehen.

## 1. Summary A valid but nondefault FTP filename encoding can restore raw CR/LF immediately before an attacker-controlled path is interpolated into the line-oriented FTP control channel. The dependency does not reject CR or LF in command arguments, so a filename can inject an independent authenticated command. A real test server observed the injected `DELE` command. The default FTP encoding and the configuration-wizard examples include `Ctl` and are not vulnerable to the demonstrated filename. A manual custom encoding that omits `Ctl`/`CrLf` is mandatory and is reflected as High attack complexity. The credible trust boundary is a lower-trust source namespace feeding a more-privileged FTP destination: if the attacker already has equivalent rights on that destination, the report establishes a bug but no privilege gain. Protocol framing must still be enforced at the command sink because a filename-compatibility encoder is not a safe substitute for command-argument validation. ## 2. Affected Assets & Attack Surface - Verified rclone revision: `a0c09f1381ae93e2a9a33c529d170186c61ad058` (`v1.74.0-240-ga0c09f138`) - Current-master check: the relevant paths remained present at commit `961266888fe797390c535386f3b3aa46f4853602` on 2026-07-18 - rclone FTP encoding: `backend/ftp/ftp.go:232-248`, `768-785` - Encoder masks/conversion: `lib/encoder/encoder.go:36-68`, `121-152`, `1144-1165` - FTP command sinks: `backend/ftp/ftp.go:1071-1173`, `1309-1428` - Dependency: `github.com/jlaffaye/ftp@v0.2.1-0.20251026020404-6602e981a1bb` - Dependency command formatting: `ftp.go:604-610`, with path-bearing callers at `ftp.go:893-947`, `1010-1026`, and `1069-1080` - Preconditions: an attacker can create a filename in a source namespace, the victim copies/syncs it to an FTP destination with greater authority, and that destination uses a manually configured encoding that leaves CR/LF raw - Platform note: Unix and some remote backends can supply newline-bearing names; a local Windows source cannot create the demonstrated filename ## 3. Technical Root Cause Analysis Rclone represents control characters safely in its internal Standard encoding. Immediately before an FTP operation, `FromStandardPath` decodes that representation and applies the configured backend mask. If the mask omits `Ctl`/`CrLf`, raw newlines are restored. The dependency then formats the resulting argument onto a CRLF-delimited control stream through `textproto.Conn.Cmd` without validating it. Reversible filename representation is therefore being used as the only protection for a protocol-command boundary. ## 4. Proof-of-Concept & Evidence The source filename was equivalent to: ```text victim\r\nDELE other-secret\r\nNOOP ``` With the default encoding, no raw newline reached the command. With the valid nondefault configuration `encoding = Slash`, `FromStandardPath` restored raw CRLF. During a real FTP path operation, the server parsed `DELE other-secret` as an independent authenticated command. This establishes injection, not merely unsafe serialization. The test did not establish confidentiality impact or operating-system command execution. ## 5. Impact Assessment Injected commands run with the configured FTP account's permissions. Demonstrated direct impact is deletion of a different path, with corresponding integrity and availability loss inside that account. Other FTP filesystem commands may be reachable, but confidentiality and arbitrary operating-system command execution are not claimed. The privilege-boundary case requires the victim's FTP account to have more authority than the attacker has in the source namespace. ## 6. Remediation Guidance - Reject CR and LF in every FTP command argument at the lowest command-construction boundary. - Apply the check to paths, usernames, passwords, rename arguments, and all other formatted fields. - Return an error rather than silently normalizing an unsafe argument. - Keep the default encoder protection as defense in depth and reject an FTP encoding configuration that can restore CR/LF. - Add end-to-end tests for CR, LF, CRLF, and each path command.

rclone is a command-line program to sync files and directories to and from different cloud storage providers. Prior to 1.75.0, a valid but nondefault FTP filename encoding in backend/ftp/ftp.go can restore raw CR/LF immediately before an attacker-controlled path is interpolated into the line-oriented FTP control channel, and github.com/jlaffaye/ftp formats the argument through textproto.Conn.Cmd without rejecting CR or LF, allowing a filename such as victim CRLF DELE other-secret CRLF NOOP to inject an independent authenticated FTP command when the victim copies or syncs to a more-privileged FTP destination. This issue is fixed in 1.75.0.

FTP command injection via custom encoding in github.com/rclone/rclone