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CVE-2026-29063

CRITICALCVSS 9.8/10EPSS 0.98%

Last modified

CVE-2026-29063 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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. EPSS estimates a 0.98% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
9.8/10

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

CVSS 4.0
8.7/10

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

EPSS Probability
0.98%

58.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
Immutable-JsImmutable>= 3.0.0, < 3.8.3
Immutable-JsImmutable>= 4.0.0, < 4.3.7
Immutable-JsImmutable>= 5.0.0, < 5.1.5

References

Timeline

Published
Last Modified
Status
Modified

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 score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.98% probability of exploitation in the next 30 days.
How do I fix CVE-2026-29063?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST