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Vulnerability · Published Mar 6, 2026 · Assigned by GitHub_M

CVE-2026-29063Immutable.js: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') in immutable

High 8.8

In plain English

A high-severity prototype pollution in immutable-js from immutable-js. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.0% (higher than 63% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.8High
Exploit odds (30 days)1.0%top 37.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12node-immutableno fix listedDEBIAN-CVE-2026-29063
Debian:13node-immutableno fix listedDEBIAN-CVE-2026-29063
Debian:14node-immutable4.3.8-1DEBIAN-CVE-2026-29063
Ubuntu:22.04:LTSnode-immutableno fix listedUBUNTU-CVE-2026-29063
Ubuntu:24.04:LTSnode-immutableno fix listedUBUNTU-CVE-2026-29063
Ubuntu:25.10node-immutableno fix listedUBUNTU-CVE-2026-29063
Ubuntu:26.04:LTSnode-immutableno fix listedUBUNTU-CVE-2026-29063
npmimmutable3.8.3GHSA-wf6x-7x77-mvgw
npmimmutable5.1.5GHSA-wf6x-7x77-mvgw
npmimmutable4.3.8GHSA-wf6x-7x77-mvgw

Affected products (as reported)

VendorProductVersions
immutable-js immutable-js < 3.8.3< 4.3.7< 5.1.5

Weakness: CWE-1321, CWE-915 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

References