CVE-2021-23436: Immer Prototype Pollution Vulnerability

CRITICAL
Advisory Identifier: GHSA-33f9-j839-rf8h
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CVSS 9.8
CWE-1321 CWE-843
Published
Advisory Summary

CVE-2021-23436 is a CRITICAL (CVSS 9.8) prototype pollution vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting Immer libraries in the npm ecosystem. The issue involves prototype pollution in immer. Remediation is available by upgrading affected packages to version 9.0.6.

CVE-2021-23436 at a Glance

CVE Identifier CVE-2021-23436
GHSA Identifier GHSA-33f9-j839-rf8h
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Product Immer
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-2021-23436

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

immer fixed: 9.0.6 
npm install immer@9.0.6
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 immer

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-23436, inspect your project dependencies using npm:

npm ls immer

Analyze the terminal output to locate any version of Immer in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 9.0.6), your application is affected.

Note: The npm ls immer 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 Immer, 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

This affects the package immer before 9.0.6. A type confusion vulnerability can lead to a bypass of CVE-2020-28477 when the user-provided keys used in the path parameter are arrays. In particular, this bypass is possible because the condition `(p === "__proto__" || p === "constructor")` in `applyPatches_` returns false if `p` is `['__proto__']` (or `['constructor']`). The `===` operator (strict equality operator) returns false if the operands have different type.

CVE-2021-23436 Affected Immer Versions

1 component(s)
Fixed Versions:
9.0.6
Product / Package Ecosystem Affected Versions Fixed Version
immer
npm/immer
npm
≥ 7.0.0
< 9.0.6
9.0.6

References

NVD — CVE-2021-23436 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-23436
Security Fix Commit FIX COMMIT
https://github.com/immerjs/immer/commit/fa671e55ee9bd42ae08cc239102b665a23958237
Immer Source Repository REPOSITORY
https://github.com/immerjs/immer
snyk.io/vuln/snyk-java-orgw... WEB
https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1579266
snyk.io/vuln/snyk-js-immer-... WEB
https://snyk.io/vuln/SNYK-JS-IMMER-1540542

Frequently Asked Questions

What is CVE-2021-23436?
CVE-2021-23436 is a security vulnerability in Immer involving Prototype Pollution in immer under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').
Which Immer versions are affected?
Affected versions include releases prior to 9.0.6 across affected packages: immer.
What version fixes CVE-2021-23436?
Upgrading to 9.0.6 (or the latest patched release for your respective branch) resolves the vulnerability.
Is immer affected?
Yes, immer is affected in releases prior to 9.0.6. Upgrade your dependency to 9.0.6 or later.
What is the CVSS score of CVE-2021-23436?
CVE-2021-23436 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-2021-23436?
CVE-2021-23436 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-2021-23436?
Run the dependency tree command: 'npm ls immer'. 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-33f9-j839-rf8h",
  "modified" : "2024-04-25T22:16:53Z",
  "published" : "2021-09-02T17:17:37Z",
  "aliases" : [ "CVE-2021-23436" ],
  "summary" : "Prototype Pollution in immer",
  "details" : "This affects the package immer before 9.0.6. A type confusion vulnerability can lead to a bypass of CVE-2020-28477 when the user-provided keys used in the path parameter are arrays. In particular, this bypass is possible because the condition `(p === \"__proto__\" || p === \"constructor\")` in `applyPatches_` returns false if `p` is `['__proto__']` (or `['constructor']`). The `===` operator (strict equality operator) returns false if the operands have different type.",
  "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" : "immer"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.0.0"
      }, {
        "fixed" : "9.0.6"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-23436"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/immerjs/immer/commit/fa671e55ee9bd42ae08cc239102b665a23958237"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/immerjs/immer"
  }, {
    "type" : "WEB",
    "url" : "https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1579266"
  }, {
    "type" : "WEB",
    "url" : "https://snyk.io/vuln/SNYK-JS-IMMER-1540542"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321", "CWE-843" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-09-02T16:57:31Z",
    "nvd_published_at" : "2021-09-01T18:15:00Z"
  }
}