CVE-2020-8131: Yarn Path Traversal Vulnerability

HIGH
Advisory Identifier: GHSA-8mfc-v7wv-p62g
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CVSS 7.5
CWE-22
Published
Advisory Summary

CVE-2020-8131 is a HIGH (CVSS 7.5) path traversal vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Yarn libraries in the npm ecosystem. The issue involves path traversal in yarn. Remediation is available by upgrading affected packages to version 1.22.0.

CVE-2020-8131 at a Glance

CVE Identifier CVE-2020-8131
GHSA Identifier GHSA-8mfc-v7wv-p62g
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Yarn
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:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H).

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

How to Fix CVE-2020-8131

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

yarn fixed: 1.22.0 
npm install yarn@1.22.0
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 yarn

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2020-8131, inspect your project dependencies using npm:

npm ls yarn

Analyze the terminal output to locate any version of Yarn in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.22.0), your application is affected.

Note: The npm ls yarn 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 Yarn, 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

Arbitrary filesystem write vulnerability in Yarn 1.21.1 and earlier allows attackers to write to any path on the filesystem and potentially lead to arbitrary code execution by forcing the user to install a malicious package.

CVE-2020-8131 Affected Yarn Versions

1 component(s)
Fixed Versions:
1.22.0
Product / Package Ecosystem Affected Versions Fixed Version
yarn
npm/yarn
npm
< 1.22.0
1.22.0

References

NVD — CVE-2020-8131 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-8131
Yarn Source Repository REPOSITORY
https://github.com/yarnpkg/yarn/pull/7831
hackerone.com/reports/730239 WEB
https://hackerone.com/reports/730239

Frequently Asked Questions

What is CVE-2020-8131?
CVE-2020-8131 is a security vulnerability in Yarn involving Path Traversal in Yarn under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Yarn versions are affected?
Affected versions include releases prior to 1.22.0 across affected packages: yarn.
What version fixes CVE-2020-8131?
Upgrading to 1.22.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is yarn affected?
Yes, yarn is affected in releases prior to 1.22.0. Upgrade your dependency to 1.22.0 or later.
What is the CVSS score of CVE-2020-8131?
CVE-2020-8131 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2020-8131?
CVE-2020-8131 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-2020-8131?
Run the dependency tree command: 'npm ls yarn'. 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-8mfc-v7wv-p62g",
  "modified" : "2021-04-08T20:35:01Z",
  "published" : "2022-02-09T22:43:37Z",
  "aliases" : [ "CVE-2020-8131" ],
  "summary" : "Path Traversal in Yarn",
  "details" : "Arbitrary filesystem write vulnerability in Yarn 1.21.1 and earlier allows attackers to write to any path on the filesystem and potentially lead to arbitrary code execution by forcing the user to install a malicious package.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "yarn"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.22.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.21.1"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-8131"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/yarnpkg/yarn/pull/7831"
  }, {
    "type" : "WEB",
    "url" : "https://hackerone.com/reports/730239"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-04-08T20:35:01Z",
    "nvd_published_at" : "2020-02-24T15:15:00Z"
  }
}