# uutils coreutils silent data loss via disabled backup mode in multiple utilities

Source: https://junglewise.ai/threats/uutils-coreutils-silent-data-loss-via-disabled-backup-mode-in-multiple-efe39da5  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-07. Updated: 2026-07-07  
License: CC BY 4.0 with a link back

Severity: high · CVSS 7 · Published 2026-07-07

A flaw in the uutils coreutils library causes several common file management tools (cp, mv, install, and ln) to fail to create backup files when the --suffix option is used by itself. This behavior differs from the standard GNU tools that users expect, leading to situations where existing files are overwritten without a backup being created. This can result in the permanent loss of important data for users or automated scripts that rely on these backups for safety.

Vendors: [crates.io](https://junglewise.ai/threats/vendors/crates-io).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** High severity, with a CVSS score of 7, published 7 July 2026.

**Which products and versions are affected?** uucore (crates.io) < 0.6.0.

**Is there a fix for This vulnerability?** A patch was published on 2025-12-21: Fixed in PR #9741 and merged into main branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked with local access, in a software library.

**Am I affected?** Check whether you run uucore (crates.io) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in the `determine_backup_mode` function within `src/uucore/src/lib/features/backup_control.rs`. The logic incorrectly returns `BackupMode::None` if only the `--suffix` flag is provided, failing to trigger the backup mechanism. In standard GNU coreutils, the presence of `--suffix` alone is sufficient to enable backup mode. This affects the `cp`, `install`, `mv`, and `ln` utilities. An attacker or a routine operation could result in unintended file overwrites (Integrity loss) because the expected backup file is never created. The issue was resolved in uucore version 0.6.0 by updating the logic to resolve the backup mode from the `$VERSION_CONTROL` environment variable when `--suffix` is present.

## Affected products

- uutils uucore < 0.6.0
- uutils coreutils < 0.6.0

## Timeline

- 2025-12-21: patched: Fixed in PR #9741 and merged into main branch
- 2026-01-20: disclosed: Reported by Zellic in security assessment for Canonical
- 2026-05-31: advisory: GitHub Advisory published

## References

- [https://github.com/uutils/coreutils/security/advisories/GHSA-fqf6-gxhh-2xhw](https://github.com/uutils/coreutils/security/advisories/GHSA-fqf6-gxhh-2xhw)
- [https://github.com/uutils/coreutils/pull/9741](https://github.com/uutils/coreutils/pull/9741)
- [https://api.github.com/repos/uutils/coreutils/security-advisories/GHSA-fqf6-gxhh-2xhw](https://api.github.com/repos/uutils/coreutils/security-advisories/GHSA-fqf6-gxhh-2xhw)

## Related threats

- [uutils coreutils TOCTOU symlink race in safe_traversal on non-Linux Unix](https://junglewise.ai/threats/cve-2026-35362-uutils-coreutils-toctou-symlink-race-in-safe-traversal-on-non)