Integer overflow in Immutable-Js Immutable
CVE-2026-59879
Immutable.js provides many Persistent Immutable data structures. Prior to 4.3.9 and 5.1.8, List#set, List#setSize, List#setIn, List#updateIn, and the functional set, setIn, and updateIn mishandle an index or size in the range 2 ** 30 to 2 ** 31 in setListBounds in src/List.js, causing an empty List to enter an uncatchable infinite loop, a populated List to allocate without bound until process abort, or setSize to silently wrap large values. This issue is fixed in versions 4.3.9 and 5.1.8.
Vulnerability class: Integer Overflow
EPSS: 0.004 (36.8th percentile) — read the EPSS interpretation.
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.
Affected products
- Immutable-js Immutable
- Immutable-js — versions >= 5.0.0-beta.1, < 5.1.8, < 4.3.9
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Mitigation, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC, Release Notes)
- security-advisories@github.com (Product, x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-59879?
- CVE-2026-59879 is a high-severity vulnerability in Immutable-Js Immutable, classified under Integer Overflow or Wraparound. CVSS score: 7.5/10. Published 2026-07-08.
- How severe is CVE-2026-59879?
- High severity. CVSS v3 base score is 7.5 out of 10.