CVE-2026-86078: n8n: Prototype Pollution via Workflow Structure Summary Can Lead to Denial of Service

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-08 · updated 2026-09-11
Weakness: CWE-1321

Description

n8n is an open source workflow automation platform. Prior to 2.37.7 and 2.38.2, the Instance AI workflow summary used node names and connection keys from stored workflows as ordinary object keys. A workflow submitted through the REST API could contain __proto__ or constructor, causing nested writes to reach Object.prototype in the main n8n process and disrupt later requests. The affected function is summarizeWorkflowStructure in packages/@n8n/instance-ai/src/tools/workflows/summarize-workflow.ts. This issue is fixed in versions 2.37.7 and 2.38.2.

Affected products

n8n-io n8n: before 2.37.7; from 2.38.0 before 2.38.2 — fixed in 2.37.7, 2.38.2

How to fix

Upgrade to a fixed version: n8n-io n8n 2.37.7, 2.38.2. Check the vendor advisory for mitigations.

References

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