CVE-2021-23421: Merge change Prototype Pollution Vulnerability

CRITICAL
Advisory Identifier: GHSA-f9cv-665r-275h
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CVSS 9.8
CWE-915
Published
Advisory Summary

CVE-2021-23421 is a CRITICAL (CVSS 9.8) prototype pollution vulnerability (CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes) affecting Merge change libraries in the npm ecosystem. The issue involves prototype pollution in merge-change. Remediation is available in the latest vendor maintenance releases.

CVE-2021-23421 at a Glance

CVE Identifier CVE-2021-23421
GHSA Identifier GHSA-f9cv-665r-275h
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes
Affected Product Merge change
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 9.8

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

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 High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2021-23421

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

merge-change fixed: Latest secure release 
npm install merge-change@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 merge-change

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-23421, inspect your project dependencies using npm:

npm ls merge-change

Analyze the terminal output to locate any version of Merge change 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 merge-change 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-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes, where the product receives input from an upstream component that specifies multiple attributes, properties, or fields that are to be initialized or updated in an object, but it does not properly control which attributes can be modified. In Merge change, 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

All current versions of package merge-change are vulnerable to Prototype Pollution via the utils.set function.

CVE-2021-23421 Affected Merge change Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
merge-change
npm/merge-change
npm
≤ 1.8.1

References

NVD — CVE-2021-23421 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-23421
Merge change Source Repository REPOSITORY
https://github.com/VladimirShestakov/merge-change
Merge change Source Repository REPOSITORY
https://github.com/VladimirShestakov/merge-change/blob/9901f145e06158f284f52de42e6ba5b0f702fb65/utils.js#L89-L123
snyk.io/vuln/snyk-js-mergec... WEB
https://snyk.io/vuln/SNYK-JS-MERGECHANGE-1310985

Frequently Asked Questions

What is CVE-2021-23421?
CVE-2021-23421 is a security vulnerability in Merge change involving Prototype Pollution in merge-change under CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes.
Which Merge change versions are affected?
Affected versions include releases prior to current release patches across affected packages: merge-change.
What version fixes CVE-2021-23421?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is merge-change affected?
Yes, merge-change 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-2021-23421?
CVE-2021-23421 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-23421?
CVE-2021-23421 is classified under CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes (The product receives input from an upstream component that specifies multiple attributes, properties, or fields that are to be initialized or updated in an object, but it does not properly control which attributes can be modified.).
How can I check npm dependencies for CVE-2021-23421?
Run the dependency tree command: 'npm ls merge-change'. 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-f9cv-665r-275h",
  "modified" : "2021-08-30T19:27:27Z",
  "published" : "2021-09-01T18:36:01Z",
  "aliases" : [ "CVE-2021-23421" ],
  "summary" : "Prototype Pollution in merge-change",
  "details" : "All current versions of package merge-change are vulnerable to Prototype Pollution via the utils.set function.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "merge-change"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "1.8.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-23421"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/VladimirShestakov/merge-change"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/VladimirShestakov/merge-change/blob/9901f145e06158f284f52de42e6ba5b0f702fb65/utils.js#L89-L123"
  }, {
    "type" : "WEB",
    "url" : "https://snyk.io/vuln/SNYK-JS-MERGECHANGE-1310985"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-915" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-30T19:27:27Z",
    "nvd_published_at" : "2021-08-11T18:15:00Z"
  }
}