In uutils coreutils, the function determine_backup_mode incorrectly returns BackupMode::None when only the --suffix option is provided, unlike GNU coreutils which enables backup mode by default in this case. This affects the cp, install, mv, and ln utilities that share this code, resulting in silent data loss when users or scripts rely on --suffix alone to create backup files before overwriting. The issue was acknowledged by Canonical and fixed in commit 939ab037a merged on 2025-12-21, included in uucore 0.6.0 and later. Regression tests were added to verify correct behavior.

Users or automated scripts relying on the --suffix option alone to create backup files before overwriting will experience silent data loss because no backup files are created. This breaks compatibility with GNU coreutils and can lead to unintended overwrites without recovery options. There is no indication of remote exploitation or privilege escalation; the impact is limited to data safety and compatibility.

A fix is available and was released in uucore version 0.6.0. Users should upgrade to version 0.6.0 or later to ensure that using --suffix alone correctly enables backup mode and prevents silent data loss. No additional mitigation is required beyond applying this official fix.