How severe is CVE-2026-29063?

CVE-2026-29063 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-29063 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-29063?

CVE-2026-29063 affects Immutable-js Immutable. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-29063?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-29063 have an EU (EUVD) identifier?

Yes. CVE-2026-29063 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-10057.

When was CVE-2026-29063 published?

CVE-2026-29063 was published on 2026-03-06 and last updated on 2026-07-02.

CVE-2026-29063

CVE-2026-29063 is a critical-severity vulnerability in Immutable-js Immutable with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1321.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v4: 8.7
EPSS exploit prediction: 1% (58th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-10057
Weakness: CWE-1321
Affected product: Immutable-js Immutable
Published: 2026-03-06
Last modified: 2026-07-02

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.

Frequently asked questions

What is CVE-2026-29063?: 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.
How severe is CVE-2026-29063?: CVE-2026-29063 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-29063 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-29063?: CVE-2026-29063 affects Immutable-js Immutable. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-29063?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-29063 have an EU (EUVD) identifier?: Yes. CVE-2026-29063 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-10057.
When was CVE-2026-29063 published?: CVE-2026-29063 was published on 2026-03-06 and last updated on 2026-07-02.

References

Affected products (1)

cpe:2.3:a:immutable-js:immutable:*:*:*:*:*:node.js:*:*

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