CVE-2026-59879
Immutable.js flaw causes uncatchable infinite loops, memory exhaustion, or size wrap via large index values.
Is CVE-2026-59879 being exploited?
Not confirmed. CVE-2026-59879 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.54% probability of exploitation in the next 30 days.
How severe is CVE-2026-59879?
CVE-2026-59879 is rated High. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-59879?
Yes. A fix has been recorded for CVE-2026-59879. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-59879 affect?
CVE-2026-59879 affects Immutable.js < 4.3.9, Immutable.js < 5.1.8, Apps using List#set, setSize, setIn, updateIn or functional equivalents. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-59879?
Upgrade to Immutable.js 4.3.9 or 5.1.8 and validate/sanitize index inputs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker-supplied large index (2^30–2^31) to List methods can trigger uncatchable infinite loop, unbounded allocation (process abort), or silent size wrap — Denial of Service / data corruption.
Patch when possible
- affected>= 5.0.0-beta.1 and < 5.1.8
- affected< 4.3.9
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.