Max Severity Ni8mare Flaw Impacts n8n Instances
CriticalExecutive Summary
A maximum severity vulnerability, dubbed Ni8mare, affects n8n instances, potentially allowing unauthenticated remote attackers to gain complete control over susceptible instances. This vulnerability is tracked as CVE-2026-21858 and has a critical status, requiring immediate attention.
Vulnerability Details
- Affected Product: n8n versions prior to 1.121.0
- Identifier: CVE-2026-21858
- CVSS Score: 10.0 (Critical)
- Exploitation Status: Details of active exploitation are not available, but the vulnerability allows unauthenticated remote code execution.
Risk & Impact
- Triage: Immediate upgrade is strongly recommended due to the severity and potential for full system compromise.
- Attack Vector: The vulnerability can be exploited by manipulating the Content-Type header in webhook requests to read arbitrary files from the system, potentially leading to remote code execution.
- Ease of Exploit: Exploitation is possible without authentication, requiring low attack complexity, which could result in full compromise of the host system.
Action Plan
- Immediate Action: Upgrade to version 1.121.0 or later to patch the vulnerability.
- Workaround: There are no official workarounds available; upgrading is the primary recommendation. Reducing external exposure of n8n instances and enforcing authentication for all forms are also advised.
- Detection: Monitor for anomalous workflow activity, unexpected process activity on automation servers, and abnormal file access.
Relevant professional terms
- Remote Code Execution (RCE)
- A vulnerability that allows an attacker to execute arbitrary code on a target system.
- CVSS Score
- A numerical score representing the severity of a vulnerability, based on metrics like exploitability and impact.
Source: bleepingcomputer.com
