Prototype Pollution in Immutable-Js Immutable
CVE-2026-29063
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.
Vulnerability class: Prototype Pollution
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.012 (68.0th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 68th percentile — 68.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.010 · newest: 0.012 · change: +0.003
Affected products
- Immutable-Js Immutable
- Immutable-Js — versions < 3.8.3, < 4.3.7, < 5.1.5
Weakness classification (CWE)
References
- github.com/immutable-js/immutable-js/security/advisories/GHSA-wf6x-7x77-mvgw (Exploit, Vendor Advisory)
- github.com/immutable-js/immutable-js/releases/tag/v3.8.3 (Release Notes)
- github.com/immutable-js/immutable-js/releases/tag/v4.3.8 (Release Notes)
- github.com/immutable-js/immutable-js/releases/tag/v5.1.5 (Release Notes)
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2026-29063?
- CVE-2026-29063 is a critical-severity vulnerability in Immutable-Js Immutable, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 9.8/10. Published 2026-03-06.
- How severe is CVE-2026-29063?
- Critical severity. CVSS v3 base score is 9.8 out of 10.