rclone’s local backend uses a configurable filename encoder to insure that remote filename data does not become operating‑system path syntax. Between releases v1.51.0 and v1.75.0, when the encoder preserves slash, backslash or uses a raw encoding, a specially crafted remote object name can contain a full‑width dot‑dot or backslash component that, after conversion, resolves to a parent directory. The subsequent filepath.Join call then writes the file outside the configured destination, allowing an attacker to create or overwrite files on the local file system. This path traversal flaw is classified as CWE‑22 and can lead to arbitrary file modification or replacement wherever the rclone process runs.

All rclone releases from version 1.51.0 through 1.74.9 (inclusive) are affected. The issue applies to the local backend on all platforms; on Windows it also occurs when the encoder preserves backslash characters. The software vendor is rclone and the vulnerability is fixed in release v1.75.0.

The CVSS score of 6.9 indicates moderate severity. No EPSS score is available, so the proven exploitation probability is unknown, and the vulnerability is not listed in CISA KEV. The attack vector is local: an attacker who can control the source objects during a sync operation can craft malicious file names that escape the destination directory. Compromise is limited to the privileges of the rclone process, but if the process runs elevated, the attacker can overwrite system files or insert malicious code.