RUSTSEC-2026-0425

Vulnerability from osv_rustsec – Published: 2026-10-30 12:00 – Updated: 2026-10-30 10:42 – Source website
VLAI
Summary
`nix-nar`: `Decoder::unpack` writes archive entries outside the destination directory (path traversal)
Details

Decoder::unpack does not safely contain the paths it extracts, so a malicious NAR archive can create files outside the destination directory — a path traversal (CWE-22).

In src/dec.rs (Decoder::unpack):

  • A symlink entry's target is written without checking where it points (src/dec.rs:153), so the archive can create a symlink that escapes the destination directory.
  • The out-of-destination containment check compares path strings only and does not account for symlinks created earlier in the same unpack (src/dec.rs:176-181), before reaching the write sinks (std::fs::create_dir at src/dec.rs:201 and OpenOptions::open at src/dec.rs:218).
  • The parser also accepts entry names containing / (src/parser.rs:138-147).

Combined, a malicious archive can include a symlink a pointing at an external directory and then an entry named a/b, causing b to be written to <external>/b, outside the destination. This can create new files anywhere the process can write (it cannot overwrite existing files), which is escalatable to code execution by planting files in attacker-chosen locations.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
References
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "categories": [
          "code-execution"
        ],
        "cvss": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
        "informational": null
      },
      "ecosystem_specific": {
        "affected_functions": null,
        "affects": {
          "arch": [],
          "functions": [
            "nix_nar::Decoder::unpack"
          ],
          "os": []
        }
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "nix-nar",
        "purl": "pkg:cargo/nix-nar"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.0.0-0"
            },
            {
              "fixed": "0.6.0"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "versions": []
    }
  ],
  "aliases": [],
  "database_specific": {
    "license": "CC0-1.0"
  },
  "details": "`Decoder::unpack` does not safely contain the paths it extracts, so a malicious NAR\narchive can create files **outside** the destination directory \u2014 a path traversal\n(CWE-22).\n\nIn `src/dec.rs` (`Decoder::unpack`):\n\n- A symlink entry\u0027s target is written without checking where it points\n  (`src/dec.rs:153`), so the archive can create a symlink that escapes the\n  destination directory.\n- The out-of-destination containment check compares path **strings** only and does\n  not account for symlinks created earlier in the same unpack\n  (`src/dec.rs:176-181`), before reaching the write sinks\n  (`std::fs::create_dir` at `src/dec.rs:201` and `OpenOptions::open` at\n  `src/dec.rs:218`).\n- The parser also accepts entry names containing `/` (`src/parser.rs:138-147`).\n\nCombined, a malicious archive can include a symlink `a` pointing at an external\ndirectory and then an entry named `a/b`, causing `b` to be written to\n`\u003cexternal\u003e/b`, outside the destination. This can create new files anywhere the\nprocess can write (it cannot overwrite existing files), which is escalatable to code\nexecution by planting files in attacker-chosen locations.",
  "id": "RUSTSEC-2026-0425",
  "modified": "2026-10-30T10:42:08Z",
  "published": "2026-10-30T12:00:00Z",
  "references": [
    {
      "type": "PACKAGE",
      "url": "https://crates.io/crates/nix-nar"
    },
    {
      "type": "ADVISORY",
      "url": "https://rustsec.org/advisories/RUSTSEC-2026-0425.html"
    },
    {
      "type": "WEB",
      "url": "https://codeberg.org/scvalex/nix-nar-rs/issues/3"
    }
  ],
  "related": [],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "`nix-nar`: `Decoder::unpack` writes archive entries outside the destination directory (path traversal)"
}



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