rclone EUVD-2026-53618

Exploitation requires three concurrent conditions to be satisfied simultaneously. First, the rclone FTP backend must be configured with a manually specified encoding that omits both Ctl and CrLf from the encoding mask - the default encoding and all configuration-wizard examples include these bits and are explicitly NOT vulnerable; only a deliberate, non-standard manual configuration creates the exposure. Second, the attacker must be able to create or place a file with a raw CR/LF sequence in its name within a source namespace that rclone syncs from - this is possible on Unix filesystems and some remote backends, but impossible from a local Windows source, which cannot create the demonstrated filename. Third, a victim with greater authority on the FTP destination must trigger a rclone copy or sync operation from the attacker-controlled source. If the attacker already holds equivalent permissions on the FTP destination, no privilege escalation occurs - the advisory notes this explicitly. Exploitation is further limited by PR:L (attacker needs source namespace write access, not anonymous access) and UI:R (victim must initiate the sync).

The provided CVSS 3.1 score of 6.4 with vector AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H accurately reflects the realistic attack constraints. AC:H is justified because the non-default manual encoding configuration is a mandatory and unlikely precondition - the default encoding and all configuration-wizard examples are not vulnerable. PR:L correctly captures that the attacker needs write access to a source namespace (not unauthenticated), and UI:R reflects that victim-triggered sync is required. The absence of confidentiality impact (C:N) is consistent with the injection technique enabling command execution (e.g., DELE) rather than data exfiltration. No EPSS score was provided in the source data, so probabilistic exploitation rate cannot be quantified. No CISA KEV listing and no standalone public exploit code were identified - only researcher-level proof-of-concept documented in the GHSA advisory. Overall, this is a genuine integrity/availability vulnerability with meaningfully bounded real-world exploitation risk: three concurrent conditions (non-default config, attacker-controlled source filenames, victim-triggered sync to a more-privileged FTP destination) must align simultaneously, and an attacker already holding equivalent FTP destination rights gains no privilege escalation.

An attacker with write access to a shared cloud storage directory creates a file named victim DELE other-secret NOOP. When a victim runs rclone to sync from that directory to an FTP server using a manually configured encoding that omits Ctl/CrLf, rclone decodes the filename to raw bytes and the FTP library forwards a control-channel string that the server parses as three independent commands - completing the intended STOR, then executing DELE other-secret with the victim's elevated FTP credentials. The GHSA advisory documents this exact sequence was observed against a real FTP test server during researcher validation.