tar-rs `unpack_in` can chmod arbitrary directories by following symlinks
Date: 2026-03
Affected: rust/tar
Attack vector: other
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-33056
CWE: CWE-61
CVSS: 6.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N)

## Summary When unpacking a tar archive, the `tar` crate's `unpack_dir` function uses `fs::metadata()` to check whether a path that already exists is a directory. Because `fs::metadata()` follows symbolic links, a crafted tarball containing a symlink entry followed by a directory entry with the same name causes the crate to treat the symlink target as a valid existing directory — and subsequently apply `chmod` to it. This allows an attacker to modify the permissions of arbitrary directories outside the extraction root. ## Reproducer A malicious tarball contains two entries: (1) a symlink `foo` pointing to an arbitrary external directory, and (2) a directory entry `foo/.` (or just `foo`). When unpacked, `create_dir("foo")` fails with `EEXIST` because the symlink is already on disk. The `fs::metadata()` check then follows the symlink, sees a directory at the target, and allows processing to continue. The directory entry's mode bits are then applied via `chmod`, which also follows the symlink — modifying the permissions of the external target directory. ## Fix The fix is very simple, we now use `fs::symlink_metadata()` in `unpack_dir`, so symlinks are detected and rejected rather than followed. ## Credit This issue was reported by @xokdvium - thank you!


Mitigations:

Architectural layers (MAESTRO):