The vulnerability lies in the dynamic-node-parameters endpoints, which did not verify that an authenticated caller was authorized to use a supplied credential reference. An authenticated user with access to a shared workflow can supply a foreign credential ID in the request body; the backend then decrypts and uses that credential in a helper execution path where the caller also controls the destination URL. This causes the backend to authenticate against attacker‑controlled infrastructure using another user's credential, allowing the attacker to exfiltrate a reusable API key. The flaw is not limited any single node type, so any dynamic credential resolution can be affected.

Affected vendors include n8n‑io with the n8n product. Any version before 1.123.33 and before 2.17.5 (and before 2.18.0) is vulnerable. The issue has been patched in n8n 1.123.33, 2.17.5, and 2.18.0 and later releases.

The CVSS score of 7.1 indicates high severity and the lack of an available EPSS score suggests limited data on exploitation frequency, while the vulnerability is not listed in the CISA KEV catalog. The likely attack vector is an authenticated user exploiting shared workflows; the attacker must have access to a workflow that references credentials. Because the flaw involves a missing authorization check (CWE‑862), an attacker can obtain a valid credential from another user, enabling the backend to make unauthorized requests to attacker‑controlled destinations.