Description

Nuclio is a "Serverless" framework for Real-Time Events and Data Processing. Prior to version 1.16.5, Nuclio Dashboard exposes POST /api/functions without authentication by default (NOP auth mode). The spec.handler field (e.g., mymodule:myfunction) is parsed by functionconfig.ParseHandler() which splits on : only — no path validation is applied to the module portion. This issue has been patched in version 1.16.5.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "4.9",
  "pubDate": "2026-09-02T17:17:45.487Z",
  "pubdate": "2026-09-02T17:17:45.487Z",
  "executiveSummary": "Nuclio versions prior to 1.16.5 contain a critical vulnerability in the Nuclio Dashboard component, specifically within the POST /api/functions endpoint.\nThe vulnerability arises due to the application operating in 'NOP' (No Operation) authentication mode by default, which fails to enforce access controls on administrative API endpoints.\nAn unauthenticated, remote attacker can leverage this oversight to interact with the function configuration API without valid credentials.\nThe core issue involves improper input validation in the functionconfig.ParseHandler() function, which fails to sanitize the module portion of the spec.handler field.\nSuccessful exploitation allows an attacker to inject arbitrary code or manipulate function execution paths, leading to full Remote Code Execution (RCE) on the underlying serverless environment.\nGiven the exposed nature of the API and the lack of authentication, the impact is severe, potentially leading to unauthorized data access, system compromise, and lateral movement within the containerized infrastructure.\nImmediate remediation requires upgrading to version 1.16.5 or later, which implements necessary input validation and enforces robust authentication mechanisms.",
  "technicalDetails": "The vulnerability is located in the Nuclio Dashboard, specifically within the API route handling function creation requests: POST /api/functions.\nThe root cause is a combination of insecure default configuration and insufficient input sanitization. When the Nuclio Dashboard is deployed in NOP authentication mode, it accepts requests to this endpoint without verifying the identity or authorization level of the requester.\nUpon receiving a request, the system processes the function configuration, specifically the 'spec.handler' field. This field is expected to follow a 'module:function' format. The backend service utilizes the 'functionconfig.ParseHandler()' function to decompose this string.\nThe 'functionconfig.ParseHandler()' implementation performs a rudimentary split operation on the ':' delimiter but lacks subsequent path validation or sanitization on the 'module' component. This deficiency allows an attacker to supply malicious input designed to traverse or point to arbitrary files within the filesystem or influence the module loading process.\nThe attack flow proceeds as follows: First, the attacker identifies a publicly accessible Nuclio Dashboard operating with NOP authentication. Second, the attacker sends a crafted POST request to '/api/functions' containing a malicious 'spec.handler' string. Third, the unvalidated payload is processed by 'functionconfig.ParseHandler()', which fails to restrict the module identifier. This allows the attacker to specify paths or modules outside the intended scope.\nBy manipulating the 'spec.handler' field, an attacker can influence how the Nuclio runtime loads and executes code. Because the application processes these configurations to deploy or update serverless functions, the attacker effectively gains the capability to inject arbitrary code into the execution environment. This behavior results in Remote Code Execution (RCE) with the privileges of the Nuclio service process.\nThis vulnerability is particularly critical because it bypasses conventional authorization boundaries. It impacts all versions prior to 1.16.5 where NOP authentication mode is active. Post-exploitation, an attacker can gain full control over the function container, access environment variables, reach internal network services, or persist within the orchestration layer."
}