n8n, an open‑source workflow automation platform, is affected by a prototype‑pollution flaw that allows an attacker to craft a public webhook payload injecting attacker‑controlled fields into workflow data during internal object copying. These injected fields are surfaced as normal values by downstream built‑in nodes, giving the workflow the ability to act as a confused deputy: it can target unintended records or issue outbound requests using the workflow owner's configured credentials. The vulnerability is fixed in n8n releases 2.25.7 and 2.26.2.

This issue affects n8n‑io's n8n platform in all releases prior to 2.25.7 and 2.26.2. Users running any earlier version that exposes public webhooks should consider this vulnerability present.

The CVSS score of 6.3 indicates medium severity. No EPSS score is available and the vulnerability is not listed in the CISA KEV catalog. Based on the description, the likely attack vector is external over the network: an attacker can send a crafted HTTP request to a public webhook endpoint and inject arbitrary properties that are subsequently processed by downstream nodes, enabling unintended execution with the workflow owner's credentials.