CVE-2026-29063
Prototype pollution in Immutable.js via mergeDeep/merge APIs.
Is CVE-2026-29063 being exploited?
Not confirmed. CVE-2026-29063 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 0.98% probability of exploitation in the next 30 days.
How severe is CVE-2026-29063?
CVE-2026-29063 is rated High with a CVSS score of 8.7. 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-2026-29063?
Yes. A fix has been recorded for CVE-2026-29063. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-29063 affect?
CVE-2026-29063 affects Immutable.js library. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-29063?
Upgrade to patched versions (3.8.3+, 4.3.7+, or 5.1.5+) immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker can pollute Object.prototype via mergeDeep/merge APIs, enabling injected properties and downstream abuse.
Immediate action required
- affected< 3.8.3
- affected< 4.3.7
- affected< 5.1.5
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.