CVE-2021-32803

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.

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.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2021-32803 has a CVSS score of 8.2 (High). The vector is requires local access, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.4.15, 5.0.7, 6.1.2, 3.2.3); upgrading removes the vulnerable code path.

Kodem intelligence

3.2.3 || 4.4.15 || 5.0.7 || 6.1.2

1. What is CVE-2021-32803? CVE-2021-32803 is a high-severity path traversal vulnerability in tar (npm), affecting versions >= 4.0.0, < 4.4.15. It is fixed in 4.4.15, 5.0.7, 6.1.2, 3.2.3. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2021-32803? CVE-2021-32803 has a CVSS score of 8.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of tar are affected by CVE-2021-32803? tar (npm) versions >= 4.0.0, < 4.4.15 is affected.
4. Is there a fix for CVE-2021-32803? Yes. CVE-2021-32803 is fixed in 4.4.15, 5.0.7, 6.1.2, 3.2.3. Upgrade to this version or later.
5. Is CVE-2021-32803 exploitable, and should I be worried? Whether CVE-2021-32803 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-32803 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-32803?
   • Upgrade tar to 4.4.15 or later
   • Upgrade tar to 5.0.7 or later
   • Upgrade tar to 6.1.2 or later
   • Upgrade tar to 3.2.3 or later