CVE-2026-39243: Decompress Decompress Allows Arbitrary Hardlink Creation Vulnerability

MODERATE
Advisory Identifier: GHSA-jwp9-9v96-94mx
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CVSS 5.5
CWE-59
Published
Advisory Summary

CVE-2026-39243 is a MODERATE (CVSS 5.5) decompress allows arbitrary hardlink creation vulnerability (CWE-59: Improper Link Resolution Before File Access ('Link Following')) affecting Decompress libraries in the npm ecosystem. The issue involves decompress allows arbitrary hardlink creation during archive extraction. Remediation is available in the latest vendor maintenance releases.

CVE-2026-39243 at a Glance

CVE Identifier CVE-2026-39243
GHSA Identifier GHSA-jwp9-9v96-94mx
Severity MODERATE
CVSS v3.1 Base Score 5.5
CWE Classification CWE-59: Improper Link Resolution Before File Access ('Link Following')
Affected Product Decompress
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.5

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:U/C:H/I:N/A:N).

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

How to Fix CVE-2026-39243

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

decompress fixed: Latest secure release 
npm install decompress@Latest secure release
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 decompress

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-39243, inspect your project dependencies using npm:

npm ls decompress

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

Note: The npm ls decompress 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-59: Improper Link Resolution Before File Access ('Link Following'), where the product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource. In Decompress, 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

decompress before 4.2.2 allows arbitrary hardlink creation during archive extraction, enabling file read disclosure and file corruption. When processing hardlink entries (type === 'link'), the x.linkname field from the archive is passed directly to fs.link() without validation (index.js line 113). An attacker can craft an archive with a hardlink entry whose linkname is an absolute path to any file on the same filesystem. This creates a hardlink inside the extraction directory that shares the same inode as the target file, enabling both reading and overwriting the original file's content. Hardlinks are limited to files on the same filesystem and cannot target directories.

CVE-2026-39243 Affected Decompress Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
decompress
npm/decompress
npm
≤ 4.2.1

References

NVD — CVE-2026-39243 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39243
Decompress Source Repository REPOSITORY
https://github.com/kevva/decompress/issues/113
Decompress Source Repository REPOSITORY
https://github.com/kevva/decompress
www.npmjs.com/package/decompress WEB
https://www.npmjs.com/package/decompress

Frequently Asked Questions

What is CVE-2026-39243?
CVE-2026-39243 is a security vulnerability in Decompress involving decompress allows arbitrary hardlink creation during archive extraction under CWE-59: Improper Link Resolution Before File Access ('Link Following').
Which Decompress versions are affected?
Affected versions include releases prior to current release patches across affected packages: decompress.
What version fixes CVE-2026-39243?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is decompress affected?
Yes, decompress is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2026-39243?
CVE-2026-39243 has a CVSS v3.1 base score of 5.5 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2026-39243?
CVE-2026-39243 is classified under CWE-59: Improper Link Resolution Before File Access ('Link Following') (The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.).
How can I check npm dependencies for CVE-2026-39243?
Run the dependency tree command: 'npm ls decompress'. 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
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-jwp9-9v96-94mx",
  "modified" : "2026-08-13T14:18:43Z",
  "published" : "2026-07-10T00:31:25Z",
  "aliases" : [ "CVE-2026-39243" ],
  "summary" : "decompress allows arbitrary hardlink creation during archive extraction",
  "details" : "decompress before 4.2.2 allows arbitrary hardlink creation during archive extraction, enabling file read disclosure and file corruption. When processing hardlink entries (type === 'link'), the x.linkname field from the archive is passed directly to fs.link() without validation (index.js line 113). An attacker can craft an archive with a hardlink entry whose linkname is an absolute path to any file on the same filesystem. This creates a hardlink inside the extraction directory that shares the same inode as the target file, enabling both reading and overwriting the original file's content. Hardlinks are limited to files on the same filesystem and cannot target directories.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "decompress"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "4.2.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-39243"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/kevva/decompress/issues/113"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/kevva/decompress"
  }, {
    "type" : "WEB",
    "url" : "https://www.npmjs.com/package/decompress"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-59" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-13T14:18:43Z",
    "nvd_published_at" : "2026-07-09T22:17:04Z"
  }
}