N8n CVE-2026-33749

Despite a moderate CVSS v4.0 score of 6.3, this vulnerability carries significant real-world risk. The attack requires authentication and social engineering (UI interaction to click a malicious link), reflected in the CVSS attributes (PR:L, UI:A). However, the scope is High (SC:H) with both integrity and confidentiality impact (VI:L, VC:L) and critical availability impact through privilege escalation (SA:H, SI:H). The vulnerability is automatable once a user clicks a link, and the technical impact—credential exfiltration and admin privilege escalation—is severe. The CVSS vector contains multiple 'X' (unknown) values indicating incomplete CVSS 4.0 scoring, suggesting this may be a preliminary assessment. Real-world prioritization should consider that exploitation requires two conditions (authenticated attacker + social engineering of higher-privileged user), making this a credible but not trivial threat. The availability of patches across three version tracks (1.123.27, 2.13.3, 2.14.1) indicates active vendor response and suggests this was responsibly disclosed via GitHub Security Advisory GHSA-qfc3-hm4j-7q77.

An authenticated n8n user with workflow editing privileges creates a malicious workflow that generates an HTML binary object containing JavaScript payload (e.g., code to exfiltrate stored credentials or modify admin settings). The attacker then crafts a URL pointing to the /rest/binary-data endpoint and socially engineers an n8n administrator to click it. When the administrator visits the URL, the browser renders the HTML inline with full JavaScript access to the n8n origin, allowing the attacker's code to steal the admin's session token, modify workflows, or escalate their own account to administrative privileges. No patch-level vulnerability code is required beyond the ability to save a workflow—the vulnerability is entirely in the endpoint's failure to sanitize output and enforce proper security headers.