CVE-2021-37712: The npm package "tar" (aka node-tar) before versions 4.4.18, 5.0.10, and 6.1.9 has an arbitrary file creation/overwrite and arbitrary code execution v...

Description

The npm package "tar" (aka node-tar) before versions 4.4.18, 5.0.10, and 6.1.9 has an arbitrary file creation/overwrite and arbitrary code execution vulnerability. 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 names containing unicode values that normalized to the same value. Additionally, on Windows systems, long path portions would resolve to the same file system entities as their 8.3 "short path" counterparts. A specially crafted tar archive could thus include a directory with one form of the path, followed by a symbolic link with a different string that resolves to the same file system entity, followed by a file using the first form. By first creating a directory, and then replacing that directory with a symlink that had a different apparent name that resolved to the same entry in the filesystem, 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. These issues were addressed in releases 4.4.18, 5.0.10 and 6.1.9. The v3 branch of node-tar has been deprecated and did not receive patches for these issues. If you are still using a v3 release we recommend you update to a more recent version of node-tar. If this is not possible, a workaround is available in the referenced GHSA-qq89-hq3f-393p.

Metrics

CVSS 3.1

8.6/10

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

EPSS Probability

1.85%

76.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Npmjs	Tar	<= 4.4.17
Npmjs	Tar	>= 5.0.0, <= 5.0.9
Npmjs	Tar	>= 6.0.0, <= 6.1.8
Debian	Debian Linux	10.0
Debian	Debian Linux	11.0
Oracle	Graalvm	20.3.3
Oracle	Graalvm	21.2.0
Siemens	Sinec Infrastructure Network Services	< 1.0.1.1

References

https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdfPatch, Third Party Advisory
https://github.com/npm/node-tar/security/advisories/GHSA-qq89-hq3f-393pPatch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2022/12/msg00023.htmlMailing List, Third Party Advisory
https://www.debian.org/security/2021/dsa-5008Third Party Advisory
https://www.npmjs.com/package/tarProduct
https://www.oracle.com/security-alerts/cpuoct2021.htmlPatch, Third Party Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdfPatch, Third Party Advisory
https://github.com/npm/node-tar/security/advisories/GHSA-qq89-hq3f-393pPatch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2022/12/msg00023.htmlMailing List, Third Party Advisory
https://www.debian.org/security/2021/dsa-5008Third Party Advisory
https://www.npmjs.com/package/tarProduct
https://www.oracle.com/security-alerts/cpuoct2021.htmlPatch, Third Party Advisory

Timeline

Published: Aug 31, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-37712?

The npm package "tar" (aka node-tar) before versions 4.4.18, 5.0.10, and 6.1.9 has an arbitrary file creation/overwrite and arbitrary code execution vulnerability. 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 names containing unicode values that normalized to the same value. Additionally, on Windows systems, long path portions would resolve to the same file system entities as their 8.3 "short path" counterparts. A specially crafted tar archive could thus include a directory with one form of the path, followed by a symbolic link with a different string that resolves to the same file system entity, followed by a file using the first form. By first creating a directory, and then replacing that directory with a symlink that had a different apparent name that resolved to the same entry in the filesystem, 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. These issues were addressed in releases 4.4.18, 5.0.10 and 6.1.9. The v3 branch of node-tar has been deprecated and did not receive patches for these issues. If you are still using a v3 release we recommend you update to a more recent version of node-tar. If this is not possible, a workaround is available in the referenced GHSA-qq89-hq3f-393p.

How severe is CVE-2021-37712?

CVE-2021-37712 has a CVSS score of 8.6/10 (HIGH severity). The EPSS model estimates a 1.85% probability of exploitation in the next 30 days.

How do I fix CVE-2021-37712?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.