GHSA-J4XF-2G29-59PH

Vulnerability from github – Published: 2026-03-20 17:25 – Updated: 2026-03-25 18:36
VLAI?
Summary
tar-rs `unpack_in` can chmod arbitrary directories by following symlinks
Details

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!

Severity ?
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
5.1 (Medium)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.4.44"
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "tar"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.4.45"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33056"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-61"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-20T17:25:09Z",
    "nvd_published_at": "2026-03-20T08:16:11Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nWhen unpacking a tar archive, the `tar` crate\u0027s `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 \u2014 and subsequently apply `chmod` to it. This allows an attacker to modify the permissions of arbitrary directories outside the extraction root.\n\n## Reproducer\n\nA 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\u0027s mode bits are then applied via `chmod`, which also follows the symlink \u2014 modifying the permissions of the external target directory.\n\n## Fix \n\nThe fix is very simple, we now use `fs::symlink_metadata()` in `unpack_dir`, so symlinks are detected and rejected rather than followed.\n\n## Credit\n\nThis issue was reported by @xokdvium - thank you!",
  "id": "GHSA-j4xf-2g29-59ph",
  "modified": "2026-03-25T18:36:33Z",
  "published": "2026-03-20T17:25:09Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/alexcrichton/tar-rs/security/advisories/GHSA-j4xf-2g29-59ph"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33056"
    },
    {
      "type": "WEB",
      "url": "https://github.com/alexcrichton/tar-rs/commit/17b1fd84e632071cb8eef9d3709bf347bd266446"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/alexcrichton/tar-rs"
    },
    {
      "type": "WEB",
      "url": "https://rustsec.org/advisories/RUSTSEC-2026-0067.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "tar-rs `unpack_in` can chmod arbitrary directories by following symlinks"
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.