A vulnerability in the chmod utility of uutils coreutils allows users to bypass the --preserve-root safety mechanism. The implementation only validates if the target path is literally / and does not canonicalize the path. An attacker or accidental user can use path variants such as /../ or symbolic links to execute destructive recursive operations (e.g., chmod -R 000) on the entire root filesystem, leading to system-wide permission loss and potential complete system breakdown.

Affected: crates.io: uu_chmod

`Chmoder::chmod()` only compares the literal argument against `Path::new("/")`, so the `--preserve-root` guard is bypassed by any path that *resolves* to root — a symlink to `/` or simply `/../`.

``` if self.recursive && self.preserve_root && file == Path::new("/") { return Err(ChmodError::PreserveRoot("/".to_string()).into()); } ```

**PoC** — recursively chmods the entire filesystem to `000` despite `--preserve-root`:

``` chmod -R --preserve-root 000 /../ -v ```

**Impact:** `--preserve-root` is the documented safeguard against destructive recursive operations on `/`. Bypassing it allows `chmod -R` to alter permissions across the whole filesystem, causing a complete system breakdown. Recommendation: canonicalize the target path before comparing against root.

**Remediation:** Acknowledged by Canonical; fixed in commit 413055b3.

--- _Reported by Zellic in the *uutils coreutils Program Security Assessment* (prepared for Canonical, Jan 20 2026), audited commit `3a07ffc5a9bd4c283e75afa548ba1f1957bad242`. Finding 3.1. Credit: Zellic._

Affected: Ubuntu:24.04:LTS: rust-coreutils, Ubuntu:25.10: rust-coreutils

A vulnerability in the chmod utility of uutils coreutils allows users to bypass the --preserve-root safety mechanism. The implementation only validates if the target path is literally / and does not canonicalize the path. An attacker or accidental user can use path variants such as /../ or symbolic links to execute destructive recursive operations (e.g., chmod -R 000) on the entire root filesystem, leading to system-wide permission loss and potential complete system breakdown.