Executive brief
rclone is a command-line program used to manage and sync files between different cloud storage providers and file servers. A vulnerability in its FTP backend allows an attacker to inject unauthorized commands by using specially crafted filenames containing newlines. If a user syncs files from a malicious source to an FTP server using a non-standard configuration, the attacker could delete files or perform other unauthorized actions on the destination server.
Technical details
A CRLF injection vulnerability exists in rclone's FTP backend when using custom filename encodings that do not mask control characters. The root cause is that rclone's 'FromStandardPath' function can restore raw CR/LF characters from internal representations before they are passed to the underlying FTP library. Because the 'github.com/jlaffaye/ftp' dependency does not validate command arguments for newlines, these characters allow an attacker to terminate the intended FTP command and start a new, arbitrary command (such as DELE). Exploitation requires the attacker to be able to create files in a source namespace that is subsequently synced to an FTP destination by a victim using a vulnerable encoding configuration. The vulnerability was patched in version 1.75.0 by implementing stricter argument validation.
Affected products
- rclone rclone < 1.75.0
Timeline
- 2026-07-31: patched: Fix released in version 1.75.0
- 2026-08-05: disclosed: Public advisory published