CVE-2021-26707: Merge deep Prototype Pollution Vulnerability

CRITICAL
Advisory Identifier: GHSA-r6rj-9ch6-g264
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CVSS 9.8
CWE-1321
Published
Advisory Summary

CVE-2021-26707 is a CRITICAL (CVSS 9.8) prototype pollution vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting Merge deep libraries in the npm ecosystem. The issue involves prototype pollution in merge-deep. Remediation is available by upgrading affected packages to version 3.0.3.

CVE-2021-26707 at a Glance

CVE Identifier CVE-2021-26707
GHSA Identifier GHSA-r6rj-9ch6-g264
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Product Merge deep
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-2021-26707

To remediate this vulnerability, upgrade all affected Merge deep 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-deep fixed: 3.0.3 
npm install merge-deep@3.0.3
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-deep

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-26707, inspect your project dependencies using npm:

npm ls merge-deep

Analyze the terminal output to locate any version of Merge deep in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.0.3), your application is affected.

Note: The npm ls merge-deep 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 Merge deep, 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 merge-deep library before 3.0.3 for Node.js can be tricked into overwriting properties of Object.prototype or adding new properties to it. These properties are then inherited by every object in the program, thus facilitating prototype-pollution attacks against applications using this library.

CVE-2021-26707 Affected Merge deep Versions

1 component(s)
Fixed Versions:
3.0.3
Product / Package Ecosystem Affected Versions Fixed Version
merge-deep
npm/merge-deep
npm
< 3.0.3
3.0.3

References

NVD — CVE-2021-26707 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-26707
Security Fix Commit FIX COMMIT
https://github.com/jonschlinkert/merge-deep/commit/11e5dd56de8a6aed0b1ed022089dbce6968d82a5
Merge deep Security Information SECURITY
https://security.netapp.com/advisory/ntap-20210716-0008
GitHub Advisory / Wiki ADVISORY
https://securitylab.github.com/advisories/GHSL-2020-160-merge-deep
www.npmjs.com/package/merge-deep WEB
https://www.npmjs.com/package/merge-deep

Frequently Asked Questions

What is CVE-2021-26707?
CVE-2021-26707 is a security vulnerability in Merge deep involving Prototype pollution in Merge-deep under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').
Which Merge deep versions are affected?
Affected versions include releases prior to 3.0.3 across affected packages: merge-deep.
What version fixes CVE-2021-26707?
Upgrading to 3.0.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is merge-deep affected?
Yes, merge-deep is affected in releases prior to 3.0.3. Upgrade your dependency to 3.0.3 or later.
What is the CVSS score of CVE-2021-26707?
CVE-2021-26707 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-2021-26707?
CVE-2021-26707 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-2021-26707?
Run the dependency tree command: 'npm ls merge-deep'. 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-r6rj-9ch6-g264",
  "modified" : "2021-06-16T19:58:45Z",
  "published" : "2021-06-07T22:09:26Z",
  "aliases" : [ "CVE-2021-26707" ],
  "summary" : "Prototype pollution in Merge-deep",
  "details" : "The merge-deep library before 3.0.3 for Node.js can be tricked into overwriting properties of Object.prototype or adding new properties to it. These properties are then inherited by every object in the program, thus facilitating prototype-pollution attacks against applications using this library.",
  "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-deep"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.0.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-26707"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jonschlinkert/merge-deep/commit/11e5dd56de8a6aed0b1ed022089dbce6968d82a5"
  }, {
    "type" : "WEB",
    "url" : "https://security.netapp.com/advisory/ntap-20210716-0008"
  }, {
    "type" : "ADVISORY",
    "url" : "https://securitylab.github.com/advisories/GHSL-2020-160-merge-deep"
  }, {
    "type" : "WEB",
    "url" : "https://www.npmjs.com/package/merge-deep"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-06-03T21:48:51Z",
    "nvd_published_at" : "2021-06-02T15:15:00Z"
  }
}