The mv utility in uutils coreutils improperly handles directory trees containing symbolic links during moves across filesystem boundaries. Instead of preserving symlinks, the implementation expands them, copying the linked targets as real files or directories at the destination. This can lead to resource exhaustion (disk space or time) if symlinks point to large external directories, unexpected duplication of sensitive data into unintended locations, or infinite recursion and repeated copying in the presence of symlink loops.

Affected: crates.io: uu_mv

When moving directories across filesystems, uutils `mv` dereferences symlinks inside the tree, copying their targets as real files/dirs instead of preserving the symlinks. GNU preserves symlinks by default. E.g. a `etc_link -> /etc` inside the source becomes a full copy of `/etc` at the destination.

**Impact:** (1) resource exhaustion — a small tree can expand into a huge copy (time/disk DoS); (2) unintended duplication of sensitive paths referenced by symlink; (3) symlink-loop amplification causing deep recursion. Recommendation: in cross-device fallback, detect symlinks via `symlink_metadata()` and recreate with `read_link()`/`symlink()`; add loop detection.

**Remediation:** Acknowledged by Canonical; fixed in commit 9654e4ab.

--- _Reported by Zellic in the *uutils coreutils Program Security Assessment* (prepared for Canonical, Jan 20 2026), audited commit `3a07ffc5a9bd4c283e75afa548ba1f1957bad242`. Finding 3.63. Credit: Zellic._

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

The mv utility in uutils coreutils improperly handles directory trees containing symbolic links during moves across filesystem boundaries. Instead of preserving symlinks, the implementation expands them, copying the linked targets as real files or directories at the destination. This can lead to resource exhaustion (disk space or time) if symlinks point to large external directories, unexpected duplication of sensitive data into unintended locations, or infinite recursion and repeated copying in the presence of symlink loops.