"The vulnerability, uncovered by researchers at security outfit Cyera, carries a CVSS score of 10.0 and has been dubbed "ni8mare" for good reason. Tracked as CVE-2026-21858, the flaw allows an unauthenticated attacker to execute arbitrary code on vulnerable systems, effectively handing over complete control of the affected environment. There is no workaround other than patching, and users are urged to upgrade to n8n version 1.121.0 or later."
"According to Cyera, the root of the problem lies in how n8n processes webhooks - the mechanism used to kick off workflows when data arrives from external systems such as web forms, messaging platforms, or notification services. By abusing a so-called "Content-Type Confusion" issue, an attacker can manipulate HTTP headers to overwrite internal variables used by the application. That, in turn, allows them to read arbitrary files from the underlying system and escalate the attack to full remote code execution."
An unauthenticated vulnerability in n8n (CVE-2026-21858) permits arbitrary code execution and full system compromise, carrying a CVSS score of 10.0. The flaw stems from how n8n processes webhooks, where a Content-Type Confusion allows attackers to manipulate HTTP headers and overwrite internal variables. Exploitation enables reading arbitrary files and escalating to remote code execution. Approximately 100,000 exposed servers may be vulnerable. No workaround exists; only upgrading to n8n version 1.121.0 or later mitigates the issue. n8n is widely self-hosted and used by millions and thousands of companies to automate workflows, increasing potential blast radius.
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