Vulnerability in Immutable-Js Immutable
CVE-2026-59880
Immutable.js provides many Persistent Immutable data structures. Prior to 4.3.9 and 5.1.8, Immutable.Map and Immutable.Set keep keys that share the same 32-bit hash in a HashCollisionNode collision bucket that is scanned linearly, allowing an attacker who controls keys inserted into a Map, such as through Immutable.Map(obj), Immutable.fromJS(obj), state.merge(userObject), or mergeDeep, to craft many colliding keys and degrade insertion and lookup to consume disproportionate CPU. This issue is fixed in versions 4.3.9 and 5.1.8.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.007 (50.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 50.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000
Affected products
- Immutable-Js Immutable
- Immutable-Js — versions < 4.3.9, >= 5.0.0-beta.1, < 5.1.8
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/immutable-js/immutable-js/security/advisories/GHSA-xvcm-6775-5m9r (Exploit, Mitigation, Vendor Advisory)
- github.com/immutable-js/immutable-js/commit/3dd7e5655012597a41873e328bf9142a890… (Patch)
- github.com/immutable-js/immutable-js/commit/e51d49fc612ded5ec4dfb94ff294d220742… (Patch)
- github.com/immutable-js/immutable-js/releases/tag/v4.3.9 (Release Notes)
- github.com/immutable-js/immutable-js/releases/tag/v5.1.8 (Release Notes)
Frequently asked questions
- What is CVE-2026-59880?
- CVE-2026-59880 is a high-severity vulnerability in Immutable-Js Immutable, classified under Inefficient Algorithmic Complexity. CVSS score: 7.5/10. Published 2026-07-08.
- How severe is CVE-2026-59880?
- High severity. CVSS v3 base score is 7.5 out of 10.
- Is CVE-2026-59880 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.