8.7

CVSS Score

4.0

-

CVSS Score

Basic Information

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CVE-2026-33011

CVE-2026-33011: Nest Fastify HEAD Request Middleware Bypass

Nest is a framework for building scalable Node.js server-side applications. In versions 11.1.15 and below, a NestJS application using @nestjs/platform-fastify GET middleware can be bypassed because Fastify automatically redirects HEAD requests to the corresponding GET handlers (if they exist). As a result: middleware will be completely skipped, the HTTP response won't include a body (since the response is truncated when redirecting a HEAD request to a GET handler), and the actual handler will still be executed. This issue is fixed in version 11.1.16.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2026-33011

CVE-2026-33011:

8.7

CVSS Score

4.0

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
@nestjs/platform-fastify	npm	<= 11.1.15	11.1.16

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability is a middleware bypass in NestJS applications using the Fastify adapter. It occurs because GET middleware is not executed for HEAD requests to GET routes. This is due to Fastify's automatic forwarding of HEAD requests to GET handlers, which was not accounted for in the middleware logic. The patch, found in commit cbdf737cd6e7cefa52d05ecea2ae4af95c464614, modifies the createProxyResolver method in packages/core/middleware/middleware-module.ts. This method returns a middleware handler. The patch alters the logic within this handler to explicitly check if a HEAD request is made to a GET route and, if so, executes the corresponding GET middleware. Therefore, MiddlewareModule.createProxyResolver is the key function to identify, as it creates the vulnerable middleware handler.

Vulnerable functions

MiddlewareModule.createProxyResolver

packages/core/middleware/middleware-module.ts

The vulnerability is in the anonymous function returned by `createProxyResolver`. This function is a middleware handler that checks if a middleware should be executed for a given request. The original implementation only checked for an exact match of the request method, causing it to skip GET middleware for HEAD requests. The patch adds a condition to also execute GET middleware when a HEAD request is received for a GET route, thus fixing the bypass.

Vulnerability Intelligence
Miggo AI

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WAF Rule

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Reasoning

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