---
title: "GHSA-r628-mhmh-qjhw: Arbitrary File Creation/Overwrite via insufficient symlink protection due to directory cache poisoning"
description: "High severity. Arbitrary File Creation/Overwrite via insufficient symlink protection due to directory cache poisoning. Affects tar; fixed in 6.1.2."
url: https://inlinr.com/advisories/GHSA-r628-mhmh-qjhw
lang: en
---

[Packages](https://inlinr.com/packages) / [tar](https://inlinr.com/packages/tar) / [Security](https://inlinr.com/packages/tar/security)

High Vulnerability GHSA-r628-mhmh-qjhw CVE-2021-32803 Published 3 Aug 2021

# Arbitrary File Creation/Overwrite via insufficient symlink protection due to directory cache poisoning

Your version 

Affected releases · [tar](https://inlinr.com/packages/tar)

- 6.x 6.0.0 – 6.1.1 Fixed in 6.1.2
- 5.x 5.0.0 – 5.0.6 Fixed in 5.0.7
- 4.x 4.0.0 – 4.4.14 Fixed in 4.4.15
- 3.x 3.0.0 – 3.2.2 Fixed in 3.2.3

On 6.x, the newest line:

```
npm install tar@6.1.2
```

Every release on a timeline

7.x 

1. Not affected

7.0.0 – 7.5.22  
33 releases, latest

6.x 

1. Affected

6.0.0 – 6.1.1  
8 releases
2. Fixed

6.1.2 – 6.2.1  
16 releases

5.x 

1. Affected

5.0.0 – 5.0.6  
7 releases
2. Fixed

5.0.7 – 5.0.11  
5 releases

4.x 

1. Affected

4.0.0 – 4.4.14  
26 releases
2. Fixed

4.4.15 – 4.4.19  
5 releases

3.x 

1. Affected

3.0.0 – 3.2.2  
21 releases
2. Fixed

3.2.3  
1 release

154 stable releases of tar, oldest to newest, one row per major.

## What happens

Impact

Arbitrary File Creation, Arbitrary File Overwrite, Arbitrary Code Execution

`node-tar` aims to guarantee that any file whose location would be modified by a symbolic link is not extracted. This is, in part, achieved by ensuring that extracted directories are not symlinks. Additionally, in order to prevent unnecessary `stat` calls to determine whether a given path is a directory, paths are cached when directories are created.

This logic was insufficient when extracting tar files that contained both a directory and a symlink with the same name as the directory. This order of operations resulted in the directory being created and added to the `node-tar` directory cache. When a directory is present in the directory cache, subsequent calls to mkdir for that directory are skipped. However, this is also where `node-tar` checks for symlinks occur.

By first creating a directory, and then replacing that directory with a symlink, it was thus possible to bypass `node-tar` symlink checks on directories, essentially allowing an untrusted tar file to symlink into an arbitrary location and subsequently extracting arbitrary files into that location, thus allowing arbitrary file creation and overwrite.

This issue was addressed in releases 3.2.3, 4.4.15, 5.0.7 and 6.1.2.

Patches

3.2.3 || 4.4.15 || 5.0.7 || 6.1.2

Workarounds

Users may work around this vulnerability without upgrading by creating a custom `filter` method which prevents the extraction of symbolic links.

```
const tar = require('tar')

tar.x({
  file: 'archive.tgz',
  filter: (file, entry) => {
    if (entry.type === 'SymbolicLink') {
      return false
    } else {
      return true
    }
  }
})
```

Users are encouraged to upgrade to the latest patch versions, rather than attempt to sanitize tar input themselves.

## How it is exploited

Exploitable with local access, with no account and a user to do something.

- **Confidentiality**: high
- **Integrity**: high
- **Availability**: none

CVSS:3.1/​AV:L/​AC:L/​PR:N/​UI:R/​S:C/​C:H/​I:H/​A:N

## References

- [Reference](https://github.com/npm/node-tar/security/advisories/GHSA-r628-mhmh-qjhw "https://github.com/npm/node-tar/security/advisories/GHSA-r628-mhmh-qjhw")  
github.com/npm/node-tar/security/advisories/GHS…
- [NVD](https://nvd.nist.gov/vuln/detail/CVE-2021-32803 "https://nvd.nist.gov/vuln/detail/CVE-2021-32803")  
nvd.nist.gov/vuln/detail/CVE-2021-32803
- [Fix commit](https://github.com/isaacs/node-tar/commit/46fe35083e2676e31c4e0a81639dce6da7aaa356 "https://github.com/isaacs/node-tar/commit/46fe35083e2676e31c4e0a81639dce6da7aaa356")  
46fe350
- [Fix commit](https://github.com/isaacs/node-tar/commit/5987d9a41f6bfbf1ddab1098e1fdcf1a5618f571 "https://github.com/isaacs/node-tar/commit/5987d9a41f6bfbf1ddab1098e1fdcf1a5618f571")  
5987d9a
- [Fix commit](https://github.com/isaacs/node-tar/commit/85d3a942b4064e4ff171f91696fced7975167349 "https://github.com/isaacs/node-tar/commit/85d3a942b4064e4ff171f91696fced7975167349")  
85d3a94
- [Fix commit](https://github.com/isaacs/node-tar/commit/9dbdeb6df8e9dbd96fa9e84341b9d74734be6c20 "https://github.com/isaacs/node-tar/commit/9dbdeb6df8e9dbd96fa9e84341b9d74734be6c20")  
9dbdeb6
- [Fix commit](https://github.com/npm/node-tar/commit/9dbdeb6df8e9dbd96fa9e84341b9d74734be6c20 "https://github.com/npm/node-tar/commit/9dbdeb6df8e9dbd96fa9e84341b9d74734be6c20")  
9dbdeb6
- [Reference](https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf "https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf")  
cert-portal.siemens.com/productcert/pdf/ssa-389…
- [Package](https://github.com/isaacs/node-tar "https://github.com/isaacs/node-tar")  
github.com/isaacs/node-tar
- [Reference](https://www.npmjs.com/advisories/1771 "https://www.npmjs.com/advisories/1771")  
npmjs.com/advisories/1771
- [Reference](https://www.npmjs.com/package/tar "https://www.npmjs.com/package/tar")  
npmjs.com/package/tar
- [Reference](https://www.oracle.com/security-alerts/cpuoct2021.html "https://www.oracle.com/security-alerts/cpuoct2021.html")  
oracle.com/security-alerts/cpuoct2021.html