CyberSecBulletin
CVE-2026-29063NVD status: Analyzed

immutable-js: Improperly Controlled Modification of Object Prototype Attributes

Published Updated By the CyberSecBulletin desk

CVE-2026-29063 is a critical-severity improperly controlled modification of object prototype attributes vulnerability in immutable-js, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected immutable-js versions: < 3.8.3; < 4.3.7; < 5.1.5. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.99% chance of exploitation within 30 days, higher than 63% of scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Check which version of immutable-js you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on github.com for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Immutable-jsimmutable-js< 3.8.3; < 4.3.7; < 5.1.5Not stated
Red HatCluster Observability Operator 1.5.0Not specified in the recordNot stated
Red HatMigration Toolkit for Virtualization 2.1Not specified in the recordNot stated
Red HatMigration Toolkit for Virtualization 2.9Not specified in the recordNot stated
Red Hatmulticluster engine for Kubernetes 2.1Not specified in the recordNot stated
Red Hatmulticluster engine for Kubernetes 2.11Not specified in the recordNot stated
Red Hatmulticluster engine for Kubernetes 2.6Not specified in the recordNot stated
Red Hatmulticluster engine for Kubernetes 2.7Not specified in the recordNot stated
Red Hatmulticluster engine for Kubernetes 2.8Not specified in the recordNot stated
Red Hatmulticluster engine for Kubernetes 2.9Not specified in the recordNot stated
Red HatNetwork Observability (NETOBSERV) 1.11.0Not specified in the recordNot stated
Red HatNetwork Observability (NETOBSERV) 1.12.2Not specified in the recordNot stated
Red HatRed Hat Advanced Cluster Management for Kubernetes 2.14Not specified in the recordNot stated
Red HatRed Hat Advanced Cluster Management for Kubernetes 2.15Not specified in the recordNot stated
Red HatRed Hat Advanced Cluster Management for Kubernetes 2.16Not specified in the recordNot stated
Red HatRed Hat Advanced Cluster Security 4.8Not specified in the recordNot stated
Red HatRed Hat Advanced Cluster Security 4.9Not specified in the recordNot stated
Red HatRed Hat Advanced Cluster Security for Kubernetes 4.10Not specified in the recordNot stated
Red HatRed Hat Developer Hub 1.8Not specified in the recordNot stated
Red HatRed Hat Developer Hub 1.9Not specified in the recordNot stated
Red HatRed Hat Discovery 2Not specified in the recordNot stated
Red HatRed Hat Edge Manager 1.0Not specified in the recordNot stated
Red HatRed Hat Edge Manager 1.1Not specified in the recordNot stated
Red HatRed Hat Migration Toolkit 1.8Not specified in the recordNot stated
Red HatRed Hat OpenShift AI 2.25Not specified in the recordNot stated

Version data comes from the organisation that assigned the CVE; 35 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 4.08.7HighCNA (github.com)
CVSS 3.19.8CriticalNVD
CVSS 3.18.8HighCNA

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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improperly Controlled Modification of Object Prototype Attributes

The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.

How developers prevent this class of flaw

  • By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.
  • By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.
  • When handling untrusted objects, validating using a schema can be used.

More Improperly Controlled Modification of Object Prototype Attributes vulnerabilities (CWE-1321)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in immutable-js

All immutable-js vulnerabilities

Recent Improperly Controlled Modification of Object Prototype Attributes vulnerabilities

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