What is CVE-2026-118678?

CVE-2026-118678 is a high-severity vulnerability in N8n-Io N8n, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 7.1/10. Published 2026-10-28.

How severe is CVE-2026-118678?

High severity. CVSS v3 base score is 7.1 out of 10.

Prototype Pollution in N8n-Io N8n

CVE-2026-118678

n8n before 2.41.4 and 2.42.x before 2.42.1 contains a prototype pollution vulnerability that allows low-privileged users to alter built-in object behaviour by saving workflows with specially named connection keys. Attackers can add keys such as __proto__ to workflow connections, which the periodic history compaction task processes, causing logins and writes to fail with server errors.

Vulnerability class: Prototype Pollution

Published 2026-10-28 · last modified 2026-10-28.

CVSS v3 metric

CVSS v3 base score 7.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

N8n-Io N8n

Weakness classification (CWE)

CWE-1321 — Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution)

References

github.com/n8n-io/n8n/security/advisories/GHSA-fvv4-gmv9-xqf5 (vendor-advisory)
www.vulncheck.com/advisories/n8n-before-2.41.4-and-2.42.1-prototype-pollution-d… (third-party-advisory)

Frequently asked questions

What is CVE-2026-118678?: CVE-2026-118678 is a high-severity vulnerability in N8n-Io N8n, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 7.1/10. Published 2026-10-28.
How severe is CVE-2026-118678?: High severity. CVSS v3 base score is 7.1 out of 10.