CVE-2018-20834: Tar Arbitrary File Overwrite Vulnerability

HIGH
Advisory Identifier: GHSA-j44m-qm6p-hp7m
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CVSS 7.5
CWE-59
Published
Advisory Summary

CVE-2018-20834 is a HIGH (CVSS 7.5) arbitrary file overwrite vulnerability (CWE-59: Improper Link Resolution Before File Access ('Link Following')) affecting Tar libraries in the npm ecosystem. The issue involves arbitrary file overwrite in tar. Remediation is available by upgrading affected packages to version 4.4.2, 2.2.2.

CVE-2018-20834 at a Glance

CVE Identifier CVE-2018-20834
GHSA Identifier GHSA-j44m-qm6p-hp7m
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-59: Improper Link Resolution Before File Access ('Link Following')
Affected Product Tar
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N).

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

How to Fix CVE-2018-20834

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: 4.4.2 
npm install tar@4.4.2
tar fixed: 2.2.2 
npm install tar@2.2.2
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-2018-20834, 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 4.4.2), 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-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 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

Versions of `tar` prior to 4.4.2 for 4.x and 2.2.2 for 2.x are vulnerable to Arbitrary File Overwrite. Extracting tarballs containing a hardlink to a file that already exists in the system, and a file that matches the hardlink will overwrite the system's file with the contents of the extracted file. ## Recommendation For tar 4.x, upgrade to version 4.4.2 or later. For tar 2.x, upgrade to version 2.2.2 or later.

CVE-2018-20834 Affected Tar Versions

2 component(s)
Fixed Versions:
4.4.22.2.2
Product / Package Ecosystem Affected Versions Fixed Version
tar
npm/tar
npm
≥ 3.0.0
< 4.4.2
4.4.2
tar
npm/tar
npm
< 2.2.2
2.2.2

References

NVD — CVE-2018-20834 NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-20834
Security Fix Commit FIX COMMIT
https://github.com/npm/node-tar/commit/7ecef07da6a9e72cc0c4d0c9c6a8e85b6b52395d
Security Fix Commit FIX COMMIT
https://github.com/npm/node-tar/commit/b0c58433c22f5e7fe8b1c76373f27e3f81dcd4c8
hackerone.com/reports/344595 WEB
https://hackerone.com/reports/344595
access.redhat.com/errata/rhsa-2019:18... WEB
https://access.redhat.com/errata/RHSA-2019:1821
Tar Source Repository REPOSITORY
https://github.com/isaacs/node-tar
Tar Source Repository REPOSITORY
https://github.com/npm/node-tar/commits/v2.2.2
Tar Source Repository REPOSITORY
https://github.com/npm/node-tar/compare/58a8d43...a5f7779

Frequently Asked Questions

What is CVE-2018-20834?
CVE-2018-20834 is a security vulnerability in Tar involving Arbitrary File Overwrite in tar under CWE-59: Improper Link Resolution Before File Access ('Link Following').
Which Tar versions are affected?
Affected versions include releases prior to 4.4.2, 2.2.2 across affected packages: tar.
What version fixes CVE-2018-20834?
Upgrading to 4.4.2, 2.2.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tar affected?
Yes, tar is affected in releases prior to 4.4.2, 2.2.2. Upgrade your dependency to 4.4.2, 2.2.2 or later.
What is the CVSS score of CVE-2018-20834?
CVE-2018-20834 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
What CWE is associated with CVE-2018-20834?
CVE-2018-20834 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-2018-20834?
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
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-j44m-qm6p-hp7m",
  "modified" : "2023-11-29T22:25:48Z",
  "published" : "2019-05-01T18:37:31Z",
  "aliases" : [ "CVE-2018-20834" ],
  "summary" : "Arbitrary File Overwrite in tar",
  "details" : "Versions of `tar` prior to 4.4.2 for 4.x and 2.2.2 for 2.x are vulnerable to Arbitrary File Overwrite. Extracting tarballs containing a hardlink to a file that already exists in the system, and a file that matches the hardlink will overwrite the system's file with the contents of the extracted file.\n\n\n## Recommendation\n\nFor tar 4.x, upgrade to version 4.4.2 or later.\nFor tar 2.x, upgrade to version 2.2.2 or later.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "tar"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.0.0"
      }, {
        "fixed" : "4.4.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "tar"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.2.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2018-20834"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/npm/node-tar/commit/7ecef07da6a9e72cc0c4d0c9c6a8e85b6b52395d"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/npm/node-tar/commit/b0c58433c22f5e7fe8b1c76373f27e3f81dcd4c8"
  }, {
    "type" : "WEB",
    "url" : "https://hackerone.com/reports/344595"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2019:1821"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/isaacs/node-tar"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/npm/node-tar/commits/v2.2.2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/npm/node-tar/compare/58a8d43...a5f7779"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-59" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2019-05-01T18:35:41Z",
    "nvd_published_at" : null
  }
}