---
id: CVE-2026-29063
title: Immutable.js provides many Persistent Immutable data structures
summary: >-
  Immutable.js provides many Persistent Immutable data structures. Prior to
  versions 3.8.3, 4.3.7, and 5.1.5, Prototype Pollution is possible in immutable
  via the mergeDeep(), mergeDeepWith(), merge(), Map.toJS(), and Map.toObject()
  APIs. …
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-1321
  - CWE-915
vendor: immutable-js
product: immutable
affected:
  - 'immutable >= 3.0.0, < 3.8.3'
  - 'immutable >= 4.0.0, < 4.3.7'
  - 'immutable >= 5.0.0, < 5.1.5'
patched:
  - immutable 5.1.5
published: '2026-03-06'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T13:18:02.623'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-29063'
references:
  - url: 'https://github.com/immutable-js/immutable-js/releases/tag/v3.8.3'
    label: security-advisories@github.com
  - url: 'https://github.com/immutable-js/immutable-js/releases/tag/v4.3.8'
    label: security-advisories@github.com
  - url: 'https://github.com/immutable-js/immutable-js/releases/tag/v5.1.5'
    label: security-advisories@github.com
  - url: >-
      https://github.com/immutable-js/immutable-js/security/advisories/GHSA-wf6x-7x77-mvgw
    label: security-advisories@github.com
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tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-03-06T19:32:37.694711Z'
scores:
  nvd: 9.8
  cna: 8.7
epss: 0.00978
epssPercentile: 0.607
ingestedAt: '2026-07-01T15:50:58.595Z'
---

## Overview

Immutable.js provides many Persistent Immutable data structures. Prior to versions 3.8.3, 4.3.7, and 5.1.5, Prototype Pollution is possible in immutable via the mergeDeep(), mergeDeepWith(), merge(), Map.toJS(), and Map.toObject() APIs. This issue has been patched in versions 3.8.3, 4.3.7, and 5.1.5.

## Affected

- `immutable >= 3.0.0, < 3.8.3`
- `immutable >= 4.0.0, < 4.3.7`
- `immutable >= 5.0.0, < 5.1.5`

## Remediation

Upgrade past the affected range:

- `immutable 5.1.5`