Cyber Resilience

CVE-2026-29063

Immutable-Js Immutable 3.0.0 – 3.8.3

Public PoC
Published
06 March 2026
Modified
13 August 2026
Patch / advisory
View advisory
CVSS Score v4 8.7
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0098 59th percentile
Risk Priority 46 floored blend · peak EPSS

Summary

CVE-2026-29063 is a high-severity Prototype Pollution (CWE-1321) vulnerability in Immutable-Js Immutable. Its CVSS base score is 8.7 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 41% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and AC-6 (Least Privilege) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-29063 is a prototype pollution vulnerability (CWE-1321) in the Immutable.js JavaScript library, which provides persistent immutable data structures. The flaw affects versions prior to 3.8.3, 4.3.7, and 5.1.5, where attackers can exploit it through the mergeDeep(), mergeDeepWith(), merge(), Map.toJS(), and Map.toObject() APIs. It has a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating critical severity due to high impacts on confidentiality, integrity, and availability.

Remote attackers require no privileges or user interaction to exploit this over the network with low complexity. Successful exploitation enables prototype pollution, allowing modification of the Object prototype and potentially leading to arbitrary code execution, denial of service, or other impacts depending on how the library is used in the application.

The issue has been patched in Immutable.js versions 3.8.3, 4.3.7, and 5.1.5, as detailed in the project's GitHub security advisory (GHSA-wf6x-7x77-mvgw) and corresponding release notes. Security practitioners should prioritize upgrading affected applications to these fixed versions to mitigate the vulnerability.

OWASP Top 10 for Web (2025)

A08:2025 Software or Data Integrity Failures

EU & UK References

Vulnerability Data

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.

CWE(s)
CWE-1321CWE-915

Related Threats

MITRE ATT&CK Enterprise Techniques

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1059 Command and Scripting Interpreter Execution
Adversaries may abuse command and script interpreters to execute commands, scripts, or binaries.
attack.mitre.org →
T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1098 Account Manipulation Persistence
Adversaries may manipulate accounts to maintain and/or elevate access to victim systems.
attack.mitre.org →
T1098.001 Additional Cloud Credentials Persistence
Adversaries may add adversary-controlled credentials to a cloud account to maintain persistent access to victim accounts and instances within the environment.
attack.mitre.org →
T1098.003 Additional Cloud Roles Persistence
An adversary may add additional roles or permissions to an adversary-controlled cloud account to maintain persistent access to a tenant.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-59879Same product: Immutable-Js Immutable
CVE-2026-59880Same product: Immutable-Js Immutable
CVE-2026-42044Shared CWE-1321, CWE-915
CVE-2026-42264Shared CWE-1321, CWE-915
CVE-2026-25521Shared CWE-1321, CWE-915
CVE-2026-42033Shared CWE-1321, CWE-915
CVE-2026-46625Shared CWE-1321, CWE-915
CVE-2026-33228Shared CWE-1321, CWE-915
CVE-2026-44494Shared CWE-1321, CWE-915
CVE-2026-42041Shared CWE-1321, CWE-915

Affected Assets

immutable-js
immutable
3.0.0 — 3.8.3 · 4.0.0 — 4.3.7 · 5.0.0 — 5.1.5

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V15.3.6

Mitigating Controls (NIST 800-53 r5) AI

AC-3 Access Enforcement good match

Enforces authorizations so that only permitted attributes may be modified on an object.

AC-6 Least Privilege good match

Limits the set of modifiable attributes a subject is authorized to touch.

SI-10 Information Input Validation good match

Validates incoming attribute names and values so that only explicitly allowed fields are accepted for update.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require input validation and safe property assignment to prevent prototype pollution.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.28 Secure coding mostly match
prevents

Secure coding standards explicitly forbid unsafe dynamic attribute assignment and require property allow-lists.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development catches prototype-pollution flaws before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle mandates input validation and object-handling controls that directly prevent prototype pollution.

A.8.26 Application security requirements partial match
prevents

Application security requirements explicitly call for safeguards against unsafe object attribute manipulation.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles reduce the likelihood of prototype pollution through safe design patterns.

A.8.3 Information access restriction partial match
prevents

Information access restriction limits who can modify objects but does not address which attributes may be changed.

References