PT-2026-23094 · Unknown+1 · Immutable-Js+1

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CVE-2026-29063

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Published

2026-03-04

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Updated

2026-07-20

CVSS v3.1

9.8

Critical

VectorAV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Name of the Vulnerable Software and Affected Versions Immutable.js versions prior to 3.8.3 Immutable.js versions prior to 4.3.7 Immutable.js versions prior to 5.1.5
Description A Prototype Pollution issue exists in Immutable.js through versions prior to 3.8.3, 4.3.7, and 5.1.5, specifically within the mergeDeep(), mergeDeepWith(), merge(), Map.toJS(), and Map.toObject() APIs. This allows for potential modification of the prototype chain, potentially leading to unexpected behavior or security compromises. The issue occurs because these APIs do not adequately guard against the introduction of properties onto the proto object during object merging or conversion. The mergeDeep() function iterates source keys via ObjectSeq and assigns merged[key]. The mergeDeepWith() function uses the same code path. The merge() function is a shallow variant with similar assignment logic. The Map.toJS() and Map.toObject() functions assign values without checking for proto properties. The Map.mergeDeep() function is also affected when the source is converted to a plain object. Proof-of-concept code demonstrates how an attacker can inject properties into the prototype chain via a crafted JSON payload, potentially escalating privileges or bypassing security checks.
Recommendations Update to Immutable.js version 3.8.3 or later. Update to Immutable.js version 4.3.7 or later. Update to Immutable.js version 5.1.5 or later.

Exploit

Fix

DoS

Prototype Pollution

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Weakness Enumeration

Related Identifiers

CVE-2026-29063
GHSA-WF6X-7X77-MVGW

Affected Products

Confluence
Immutable-Js