Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-29063

CVE-2026-29063HIGH

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

  AV  AC  AT  PR  UI  VC  VI  VA   CVSS    EPSS   %ile   KEV
   N   L   N   N   N   H   N   N    8.7   .0161   75.0     —

AFFECTED
  Product       Versions   Fixed
  immutable-js  < 3.8.3 –  —

TIMELINE
  Mar 3   Reserved by GitHub_M
  Mar 6   Published (CNA: GitHub_M)
  Aug 24  EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
  Aug 25  EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
  Aug 26  EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
  Aug 31  EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
  Sep 4   EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
  Sep 7   EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
  Sep 9   EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
  Sep 10  EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.

CWE-1321, CWE-915 · CNA: GitHub_M · CVSS v4.0 · 72 references · NVD status: Modified

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.

Lifecycle

Complete event history — 10 events, chronological
Date	Event	Detail
March 3, 2026	Reserved	Reserved by GitHub_M
March 6, 2026	Published	Published (CNA: GitHub_M)
August 24, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
August 25, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
August 26, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
August 31, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
September 4, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
September 7, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
September 9, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.
September 10, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-29063 (immutable-js). Public exploit reference added.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
immutable-js	immutable-js	—	< 3.8.3	—

Weaknesses

CWE-1321 · CWE-915

References (72)

Authoritative record: CVE-2026-29063 at cve.org

Vendors: immutable-js

Weaknesses: CWE-1321 · CWE-915

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-29063 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.