CVE-2021-37712 | Arbitrary File Creation/Overwrite via insufficient symlink protection due to directory cache poisoning using symbolic links

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.

Published: 2021-08-31 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-37712 is rated Moderate Risk (60.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.72%). EPSS rose +1.63% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-37712

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.09% 1.72% +1.63%
2 2026-03-03 0.02% 0.09% +0.07%
3 2025-11-21 — 0.02% —

Full EPSS history (19 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-37712

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.2 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 1.8 5.8 [email protected]
8.6 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 6.0 [email protected]
4.4 2.0 MEDIUM
AV:L/AC:M/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:L)
Requires local access to the target system.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 3.4 6.4 [email protected]

Weakness enumeration for CVE-2021-37712

GitHub Security Advisory for CVE-2021-37712

GHSA-qq89-hq3f-393p · Severity: high · Ecosystem: npm — Arbitrary File Creation/Overwrite via insufficient symlink protection due to directory cache poisoning using symbolic links

OS Trackers for CVE-2021-37712

vendor priority summary link
alpine high CVE-2021-37712: 1 source package rows (nodejs); 9 state rows across 9 repos (3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 9, open 0. https://security.alpinelinux.org/vuln/CVE-2021-37712
debian not yet assigned CVE-2021-37712 not yet assigned priority: Debian including 1 source packages (node-tar), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-37712
gentoo low CVE-2021-37712: 1 GLSA(s) (202405-29), 1 atom(s) (net-libs/nodejs); latest impact low. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-37712
redhat medium — https://access.redhat.com/security/cve/CVE-2021-37712
suse high CVE-2021-37712 severity important: SUSE including 39 source package names (12-10.1:nodejs12-12.22.7-4.22.1, 12-10.1:npm12-12.22.7-4.22.1, …), 91 product×package rows across 11 product lines (Container bci/nodejs, SUSE Liberty Linux 8, … (11 product lines)): Fixed 83, Known Not Affected 8. https://www.suse.com/security/cve/CVE-2021-37712/
ubuntu medium CVE-2021-37712 medium priority: Ubuntu including 1 source packages (node-tar), 15 status rows across 15 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): needs-triage 8, ignored 7. https://ubuntu.com/security/CVE-2021-37712

Affected software / configurations for CVE-2021-37712

Vendor Product Version Raw CPE
npmjs tar <= 4.4.17 cpe:2.3:a:npmjs:tar:*:*:*:*:*:node.js:*:*
npmjs tar >= 5.0.0, <= 5.0.9 cpe:2.3:a:npmjs:tar:*:*:*:*:*:node.js:*:*
npmjs tar >= 6.0.0, <= 6.1.8 cpe:2.3:a:npmjs:tar:*:*:*:*:*:node.js:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
debian debian_linux 11.0 cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
oracle graalvm 20.3.3 cpe:2.3:a:oracle:graalvm:20.3.3:*:*:*:enterprise:*:*:*
oracle graalvm 21.2.0 cpe:2.3:a:oracle:graalvm:21.2.0:*:*:*:enterprise:*:*:*
siemens sinec_infrastructure_network_services < 1.0.1.1 cpe:2.3:a:siemens:sinec_infrastructure_network_services:*:*:*:*:*:*:*:*

References for CVE-2021-37712

cvelogic Threat Intelligence