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CVE Record

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

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.

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-29063 affects Immutable.js, a JavaScript library used in web and Node.js applications. Certain merge and object-conversion APIs can allow prototype pollution before the fixed versions. In business terms, applications that process attacker-controlled data through these APIs may face data tampering, service disruption, or broader compromise depending on usage.

Executive priority

Treat as high priority for internet-facing or data-processing JavaScript services. It is not confirmed as actively exploited in the provided sources, but the high CVSS score and common dependency pattern justify prompt inventory and upgrade work.

Technical view

Immutable.js before 3.8.3, 4.3.7, and 5.1.5 is vulnerable through mergeDeep(), mergeDeepWith(), merge(), Map.toJS(), and Map.toObject(). The issue is classified as CWE-1321 and CWE-915, with CVSS 8.8. The source bundle does not provide exploit details or application-specific prerequisites beyond low complexity and required privileges.

Likely exposure

Exposure is most likely in JavaScript or Node.js applications that include immutable or immutable-js versions below 3.8.3, 4.3.7, or 5.1.5 and pass untrusted structured data into the listed APIs.

Exploitation context

The source bundle marks KEV as false and provides no cited evidence of active exploitation. The CVSS vector indicates network reachability, low attack complexity, low privileges, and no user interaction, but real impact depends on how the library is used.

Researcher notes

The public bundle identifies affected APIs and fixed versions but does not include proof-of-concept material, exploit telemetry, or detailed vulnerable data-flow examples. Validation should focus on dependency resolution and whether untrusted object data reaches the affected Immutable.js APIs.

Mitigation direction

  • Upgrade Immutable.js to 3.8.3, 4.3.7, 5.1.5, or later as applicable.
  • Check vendor guidance for any Red Hat-packaged exposure and errata applicability.
  • Prioritize applications processing untrusted JSON or request bodies with the listed APIs.
  • Review dependency overrides or transitive dependencies that may pin vulnerable versions.

Validation and detection

  • Inventory package manifests, lockfiles, and SBOMs for immutable or immutable-js versions.
  • Confirm resolved versions meet the fixed release thresholds for the used major branch.
  • Review code paths using mergeDeep, mergeDeepWith, merge, Map.toJS, or Map.toObject.
  • Check whether attacker-controlled structured data reaches those APIs.
  • Verify CI or dependency scanning reports no vulnerable Immutable.js instances remain.
Prepared
Confidence
high
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-1321: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-915: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-29063 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
8.8 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
45Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.8CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9redhat-SADP
8.7CVSS 4.0HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N——GitHub_M

Vulnerability scoring details

Base CVSS 4.0 score

8.7High
CVSS 4.0 vector shape for CVE-2026-29063Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPimmutable-js: Immutable.js: Arbitrary code execution via Prototype Pollution
other:Red Hat severity ratingcvssV3_1
  • 2026-03-06T19:00:57.982Z: Reported to Red Hat.
  • 2026-03-06T18:25:22.438Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
immutable-jsimmutable-js< 3.8.3, < 4.3.7, < 5.1.5Listed
Weakness

CWE details

CWE-1321CWE-915

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-1321 · source CWE mapping

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-915 · source CWE mapping

Improperly Controlled Modification of Dynamically-Determined Object Attributes

Improperly Controlled Modification of Dynamically-Determined Object Attributes represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs