CVE-2021-37713: Tar Arbitrary File Creation/Overwrite On Windows Vulnerability

HIGH
Advisory Identifier: GHSA-5955-9wpr-37jh
CVSS 8.2
CWE-22
Published
Advisory Summary

CVE-2021-37713 is a HIGH (CVSS 8.2) arbitrary file creation/overwrite on windows vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Tar libraries in the npm ecosystem. The issue involves arbitrary file creation/overwrite on windows via insufficient relative path sanitization. Remediation is available by upgrading affected packages to version 4.4.18, 5.0.10, 6.1.9.

CVE-2021-37713 at a Glance

CVE Identifier CVE-2021-37713
GHSA Identifier GHSA-5955-9wpr-37jh
Severity HIGH
CVSS v3.1 Base Score 8.2
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Tar
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 8.2

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N).

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2021-37713

To remediate this vulnerability, upgrade all affected Tar dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

tar fixed: 4.4.18
npm install tar@4.4.18
tar fixed: 5.0.10
npm install tar@5.0.10
tar fixed: 6.1.9
npm install tar@6.1.9
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release:

npm ls tar

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-37713, inspect your project dependencies using npm:

npm ls tar

Analyze the terminal output to locate any version of Tar in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.4.18), your application is affected.

Note: The npm ls tar command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. In Tar, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Arbitrary File Creation, Arbitrary File Overwrite, Arbitrary Code Execution node-tar aims to guarantee that any file whose location would be outside of the extraction target directory is not extracted. This is, in part, accomplished by sanitizing absolute paths of entries within the archive, skipping archive entries that contain `..` path portions, and resolving the sanitized paths against the extraction target directory. This logic was insufficient on Windows systems when extracting tar files that contained a path that was not an absolute path, but specified a drive letter different from the extraction target, such as `C:some\path`. If the drive letter does not match the extraction target, for example `D:\extraction\dir`, then the result of `path.resolve(extractionDirectory, entryPath)` would resolve against the current working directory on the `C:` drive, rather than the extraction target directory. Additionally, a `..` portion of the path could occur immediately after the drive letter, such as `C:../foo`, and was not properly sanitized by the logic that checked for `..` within the normalized and split portions of the path. This only affects users of `node-tar` on Windows systems. ### Patches 4.4.18 || 5.0.10 || 6.1.9 ### Workarounds There is no reasonable way to work around this issue without performing the same path normalization procedures that node-tar now does. Users are encouraged to upgrade to the latest patched versions of node-tar, rather than attempt to sanitize paths themselves. ### Fix The fixed versions strip path roots from all paths prior to being resolved against the extraction target folder, even if such paths are not "absolute". Additionally, a path starting with a drive letter and then two dots, like `c:../`, would bypass the check for `..` path portions. This is checked properly in the patched versions. Finally, a defense in depth check is added, such that if the `entry.absolute` is outside of the extraction taret, and we are not in preservePaths:true mode, a warning is raised on that entry, and it is skipped. Currently, it is believed that this check is redundant, but it did catch some oversights in development.

CVE-2021-37713 Affected Tar Versions

3 component(s)
Fixed Versions:
4.4.185.0.106.1.9
Product / Package Ecosystem Affected Versions Fixed Version
tar
npm
< 4.4.18
4.4.18
tar
npm
≥ 5.0.0
< 5.0.10
5.0.10
tar
npm
≥ 6.0.0
< 6.1.9
6.1.9

References

Frequently Asked Questions

What is CVE-2021-37713?
CVE-2021-37713 is a security vulnerability in Tar involving Arbitrary File Creation/Overwrite on Windows via insufficient relative path sanitization under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Tar versions are affected?
Affected versions include releases prior to 4.4.18, 5.0.10, 6.1.9 across affected packages: tar.
What version fixes CVE-2021-37713?
Upgrading to 4.4.18, 5.0.10, 6.1.9 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tar affected?
Yes, tar is affected in releases prior to 4.4.18, 5.0.10, 6.1.9. Upgrade your dependency to 4.4.18, 5.0.10, 6.1.9 or later.
What is the CVSS score of CVE-2021-37713?
CVE-2021-37713 has a CVSS v3.1 base score of 8.2 (HIGH) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N.
What CWE is associated with CVE-2021-37713?
CVE-2021-37713 is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.).
How can I check npm dependencies for CVE-2021-37713?
Run the dependency tree command: 'npm ls tar'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
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  "id" : "GHSA-5955-9wpr-37jh",
  "modified" : "2021-08-31T16:02:32Z",
  "published" : "2021-08-31T16:05:05Z",
  "aliases" : [ "CVE-2021-37713" ],
  "summary" : "Arbitrary File Creation/Overwrite on Windows via insufficient relative path sanitization",
  "details" : "### Impact\n\nArbitrary File Creation, Arbitrary File Overwrite, Arbitrary Code Execution\n\nnode-tar aims to guarantee that any file whose location would be outside of the extraction target directory is not extracted. This is, in part, accomplished by sanitizing absolute paths of entries within the archive, skipping archive entries that contain `..` path portions, and resolving the sanitized paths against the extraction target directory.\n\nThis logic was insufficient on Windows systems when extracting tar files that contained a path that was not an absolute path, but specified a drive letter different from the extraction target, such as `C:some\\path`.  If the drive letter does not match the extraction target, for example `D:\\extraction\\dir`, then the result of `path.resolve(extractionDirectory, entryPath)` would resolve against the current working directory on the `C:` drive, rather than the extraction target directory.\n\nAdditionally, a `..` portion of the path could occur immediately after the drive letter, such as `C:../foo`, and was not properly sanitized by the logic that checked for `..` within the normalized and split portions of the path.\n\nThis only affects users of `node-tar` on Windows systems.\n\n### Patches\n\n4.4.18 || 5.0.10 || 6.1.9\n\n### Workarounds\n\nThere is no reasonable way to work around this issue without performing the same path normalization procedures that node-tar now does.\n\nUsers are encouraged to upgrade to the latest patched versions of node-tar, rather than attempt to sanitize paths themselves.\n\n### Fix\n\nThe fixed versions strip path roots from all paths prior to being resolved against the extraction target folder, even if such paths are not \"absolute\".\n\nAdditionally, a path starting with a drive letter and then two dots, like `c:../`, would bypass the check for `..` path portions.  This is checked properly in the patched versions.\n\nFinally, a defense in depth check is added, such that if the `entry.absolute` is outside of the extraction taret, and we are not in preservePaths:true mode, a warning is raised on that entry, and it is skipped.  Currently, it is believed that this check is redundant, but it did catch some oversights in development.\n",
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}