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.
References
Chmoder::chmod()only compares the literal argument againstPath::new("/"), so the--preserve-rootguard is bypassed by any path that resolves to root — a symlink to/or simply/../.PoC — recursively chmods the entire filesystem to
000despite--preserve-root:Impact:
--preserve-rootis the documented safeguard against destructive recursive operations on/. Bypassing it allowschmod -Rto 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.References