Review reviewHigh

CVE-2026-29063

immutable-js immutable-js, Cluster Observability Operator 1.5.0, Migration Toolkit for Virtualization 2.1

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.

CVSS: 8.7
EPSS: 0.98%
CISA KEV: Not listed
Published: 2026.03.07

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability0.98%

Technical severityCVSS 8.7

Vulnerability overview

Affected product and versions

Product: immutable-js immutable-js, Cluster Observability Operator 1.5.0, Migration Toolkit for Virtualization 2.1
Affected versions: >= < 3.8.3, >= < 4.3.7, >= < 5.1.5, >= 3.0.0 < 3.8.3, >= 4.0.0 < 4.3.7, >= 5.0.0 < 5.1.5
Fixed versions: 3.8.3, 4.3.7, 5.1.5

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that immutable-js immutable-js, Cluster Observability Operator 1.5.0, Migration Toolkit for Virtualization 2.1 and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS 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/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
CWE: CWE-1321, CWE-915