n8n Fixes Credential Exfiltration and Multiple Access Control Flaws

n8n published security advisories for multiple supported release branches after disclosure of several vulnerabilities, including a critical flaw tracked as CVE-2026-56348. The CVE affects versions before 2.20.0 and allows an authenticated user to abuse the POST /rest/dynamic-node-parameters/options endpoint to bypass Allowed HTTP Request Domains restrictions, causing the server to send credential-bearing HTTP requests to unauthorized hosts and potentially exfiltrate sensitive authentication data. The issue is remotely exploitable and impacts environments where users can access affected dynamic node functionality.

The broader advisory set also covers additional n8n weaknesses in releases prior to 2.28.1, 2.27.4, and 1.123.61, including another Allowed HTTP Request Domains bypass through the AI Agents MCP Connector, prototype pollution via workflow credentials that can lead to unauthenticated user and project enumeration, cross-issuer token exchange account binding caused by subject-only identity resolution, and a shared credential header leak through HTTP request pagination expressions. The Canadian Centre for Cyber Security urged administrators to review the advisories, upgrade to the patched versions, restrict access to exposed endpoints where possible, and monitor for unauthorized outbound requests that could indicate credential leakage.