CVE-2021-23568: Extend2 Prototype Pollution Vulnerability

HIGH
Advisory Identifier: GHSA-gjm5-83cw-p3p2
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CVSS 7.3
CWE-1321
Published
Advisory Summary

CVE-2021-23568 is a HIGH (CVSS 7.3) prototype pollution vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting Extend2 libraries in the npm ecosystem. The issue involves prototype pollution in extend2. Remediation is available by upgrading affected packages to version 1.0.1.

CVE-2021-23568 at a Glance

CVE Identifier CVE-2021-23568
GHSA Identifier GHSA-gjm5-83cw-p3p2
Severity HIGH
CVSS v3.1 Base Score 7.3
CWE Classification CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Product Extend2
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.3

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:L/I:L/A:L).

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 Low (C:L)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2021-23568

To remediate this vulnerability, upgrade all affected Extend2 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

extend2 fixed: 1.0.1 
npm install extend2@1.0.1
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 extend2

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-23568, inspect your project dependencies using npm:

npm ls extend2

Analyze the terminal output to locate any version of Extend2 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.0.1), your application is affected.

Note: The npm ls extend2 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 Extend2, 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

The package extend2 before 1.0.1 are vulnerable to Prototype Pollution via the extend function due to unsafe recursive merge.

CVE-2021-23568 Affected Extend2 Versions

1 component(s)
Fixed Versions:
1.0.1
Product / Package Ecosystem Affected Versions Fixed Version
extend2
npm/extend2
npm
< 1.0.1
1.0.1

References

NVD — CVE-2021-23568 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-23568
Extend2 Source Repository REPOSITORY
https://github.com/eggjs/extend2/pull/2
Security Fix Commit FIX COMMIT
https://github.com/eggjs/extend2/commit/aa332a59116c8398976434b57ea477c6823054f8
Extend2 Source Repository REPOSITORY
https://github.com/eggjs/extend2
Extend2 Source Repository REPOSITORY
https://github.com/eggjs/extend2/blob/master/index.js%23L50-L60
snyk.io/vuln/snyk-js-extend... WEB
https://snyk.io/vuln/SNYK-JS-EXTEND2-2320315

Frequently Asked Questions

What is CVE-2021-23568?
CVE-2021-23568 is a security vulnerability in Extend2 involving Prototype Pollution in extend2 under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').
Which Extend2 versions are affected?
Affected versions include releases prior to 1.0.1 across affected packages: extend2.
What version fixes CVE-2021-23568?
Upgrading to 1.0.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is extend2 affected?
Yes, extend2 is affected in releases prior to 1.0.1. Upgrade your dependency to 1.0.1 or later.
What is the CVSS score of CVE-2021-23568?
CVE-2021-23568 has a CVSS v3.1 base score of 7.3 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L.
What CWE is associated with CVE-2021-23568?
CVE-2021-23568 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-2021-23568?
Run the dependency tree command: 'npm ls extend2'. 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-gjm5-83cw-p3p2",
  "modified" : "2022-01-11T18:11:48Z",
  "published" : "2022-01-12T22:59:13Z",
  "aliases" : [ "CVE-2021-23568" ],
  "summary" : "Prototype Pollution in extend2",
  "details" : "The package extend2 before 1.0.1 are vulnerable to Prototype Pollution via the extend function due to unsafe recursive merge.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "extend2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.0.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-23568"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/eggjs/extend2/pull/2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/eggjs/extend2/commit/aa332a59116c8398976434b57ea477c6823054f8"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/eggjs/extend2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/eggjs/extend2/blob/master/index.js%23L50-L60"
  }, {
    "type" : "WEB",
    "url" : "https://snyk.io/vuln/SNYK-JS-EXTEND2-2320315"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-01-11T18:11:48Z",
    "nvd_published_at" : "2022-01-10T14:10:00Z"
  }
}