CVE-2018-3721: Lodash Prototype Pollution Vulnerability

MODERATE
Advisory Identifier: GHSA-fvqr-27wr-82fm
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CVSS 6.5
CWE-1321 CWE-471
Published
Advisory Summary

CVE-2018-3721 is a MODERATE (CVSS 6.5) prototype pollution vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting Lodash libraries in the npm ecosystem. The issue involves prototype pollution in lodash. Remediation is available by upgrading affected packages to version 4.17.5.

CVE-2018-3721 at a Glance

CVE Identifier CVE-2018-3721
GHSA Identifier GHSA-fvqr-27wr-82fm
Severity MODERATE
CVSS v3.1 Base Score 6.5
CWE Classification CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Product Lodash
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 6.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
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-2018-3721

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

lodash fixed: 4.17.5 
npm install lodash@4.17.5
lodash-rails fixed: 4.17.5 
Upgrade lodash-rails to 4.17.5
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 lodash

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2018-3721, inspect your project dependencies using npm:

npm ls lodash

Analyze the terminal output to locate any version of Lodash in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.17.5), your application is affected.

Note: The npm ls lodash 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-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution'), where the product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. In Lodash, 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 `lodash` before 4.17.5 are vulnerable to prototype pollution. The vulnerable functions are 'defaultsDeep', 'merge', and 'mergeWith' which allow a malicious user to modify the prototype of `Object` via `__proto__` causing the addition or modification of an existing property that will exist on all objects. ## Recommendation Update to version 4.17.5 or later.

CVE-2018-3721 Affected Lodash Versions

2 component(s)
Fixed Versions:
4.17.5
Product / Package Ecosystem Affected Versions Fixed Version
lodash
npm/lodash
npm
< 4.17.5
4.17.5
lodash-rails
gem/lodash-rails
RubyGems
< 4.17.5
4.17.5

References

NVD — CVE-2018-3721 NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-3721
Security Fix Commit FIX COMMIT
https://github.com/lodash/lodash/commit/d8e069cc3410082e44eb18fcf8e7f3d08ebe1d4a
hackerone.com/reports/310443 WEB
https://hackerone.com/reports/310443
Lodash Source Repository REPOSITORY
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/lodash-rails/CVE-2018-3721.yml
Lodash Security Information SECURITY
https://security.netapp.com/advisory/ntap-20190919-0004

Frequently Asked Questions

What is CVE-2018-3721?
CVE-2018-3721 is a security vulnerability in Lodash involving Prototype Pollution in lodash under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').
Which Lodash versions are affected?
Affected versions include releases prior to 4.17.5 across affected packages: lodash, lodash-rails.
What version fixes CVE-2018-3721?
Upgrading to 4.17.5 (or the latest patched release for your respective branch) resolves the vulnerability.
Is lodash affected?
Yes, lodash is affected in releases prior to 4.17.5. Upgrade your dependency to 4.17.5 or later.
Is lodash-rails affected?
Yes, lodash-rails is affected in releases prior to 4.17.5. Upgrade your dependency to 4.17.5 or later.
What is the CVSS score of CVE-2018-3721?
CVE-2018-3721 has a CVSS v3.1 base score of 6.5 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N.
What CWE is associated with CVE-2018-3721?
CVE-2018-3721 is classified under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.).
How can I check npm dependencies for CVE-2018-3721?
Run the dependency tree command: 'npm ls lodash'. 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-fvqr-27wr-82fm",
  "modified" : "2025-08-12T21:37:06Z",
  "published" : "2018-07-26T15:14:52Z",
  "aliases" : [ "CVE-2018-3721" ],
  "summary" : "Prototype Pollution in lodash",
  "details" : "Versions of `lodash` before 4.17.5 are vulnerable to prototype pollution. \n\nThe vulnerable functions are 'defaultsDeep', 'merge', and 'mergeWith' which allow a malicious user to modify the prototype of `Object` via `__proto__` causing the addition or modification of an existing property that will exist on all objects.\n\n\n\n\n## Recommendation\n\nUpdate to version 4.17.5 or later.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "lodash"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.17.5"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "lodash-rails"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.17.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2018-3721"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/lodash/lodash/commit/d8e069cc3410082e44eb18fcf8e7f3d08ebe1d4a"
  }, {
    "type" : "WEB",
    "url" : "https://hackerone.com/reports/310443"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/lodash-rails/CVE-2018-3721.yml"
  }, {
    "type" : "WEB",
    "url" : "https://security.netapp.com/advisory/ntap-20190919-0004"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321", "CWE-471" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-06-16T21:35:26Z",
    "nvd_published_at" : "2018-06-07T02:29:08Z"
  }
}