n8n CVE-2026-118678

Requires an authenticated low-privileged account with permission to create and save workflows (PR:L), and requires the workflow-history feature to be enabled (default), since the periodic workflow-history compaction task is what processes the connections object and triggers the prototype pollution. The specific trigger is a workflow connections key named with a reserved JavaScript property such as __proto__, constructor, or prototype. Limiting factors: exploitation is not possible by fully unauthenticated attackers, is neutralized by setting N8N_WORKFLOW_HISTORY_ENABLED=false where history is not needed, and is bounded to instances running n8n before 2.41.4 or 2.42.x before 2.42.1; restricting instance access to fully trusted users also limits exposure (per the vendor, these workarounds are temporary and do not fully remediate - upgrading is the complete fix).

The vuln.today priority is 'this_week' and the supplied CVSS 4.0 vector scores 7.1, but the real-world risk is moderate and gated by preconditions rather than critical. The vector is AV:N/AC:L/AT:N/PR:L/UI:N with impact VC:N/VI:L/VA:H - meaning network-reachable and low-complexity, but requiring an authenticated low-privileged account (PR:L) and yielding no confidentiality loss, only low integrity and high availability impact (a denial-of-service that breaks logins and writes). This is squarely a DoS/integrity issue, not data theft or code execution, so despite the 'high' severity band it is not a drive-by, unauthenticated catastrophe. No EPSS score was provided in the input, so exploitation probability cannot be quantified. The CVE is NOT in CISA KEV and no exploit/PoC code is referenced (only the vendor GHSA and VulnCheck advisories), so there is no evidence of active exploitation or published weaponized code. Net: a legitimate patch-this-week item for any multi-tenant or lower-trust n8n deployment because any user who can save a workflow can disrupt the whole instance, but lower urgency for single-admin or fully-trusted installations. Note the input Tags claim 'Information Disclosure', which conflicts with the CVSS impact (VC:N = no confidentiality impact) and the advisory title describing denial of service - treat the DoS characterization as authoritative.

A low-privileged but authenticated n8n user creates and saves a workflow whose connections object contains a reserved key such as __proto__. When the periodic workflow-history compaction task later diffs that connections object, it pollutes the global Object prototype, after which the whole n8n process begins returning server errors for logins and writes - a denial of service affecting all users. No public exploit code is referenced in the available sources; exploitation requires only the ability to save a workflow.