CVE-2026-14181

HIGH

@fastify/middie standalone engine vulnerable to Denial of Service via malformed percent-encoded paths

Title source: cna
STIX 2.1

Exploitation Summary

EIP tracks 1 public exploit for CVE-2026-14181. PoCs published by HermesNA-1.

AI-analyzed exploit summary This repository contains an auto-generated stub module for CVE-2026-14181, a vulnerability in @fastify/middie versions 9.1.0 through 9.3.2. The module includes placeholder code for probing target connectivity but lacks actual exploit implementation for the URL normalization flaw.

Description

@fastify/middie versions 9.1.0 through 9.3.2 fail to guard the URL normalization step used by the standalone engine when incoming request paths contain malformed percent-encoded sequences. Inputs such as an incomplete percent escape or a truncated multibyte sequence cause the underlying decoder to throw synchronously, and the exception escapes the middie normalize step and terminates the Node.js process. The bypass affects applications that call middie.run directly on the standalone engine API, causing an immediate denial of service for all connected clients until restart. Applications using the Fastify plugin path are not affected because Fastifys error handler catches the exception. Patches: upgrade to @fastify/middie 9.3.3. Workarounds: migrate from the standalone engine API to the Fastify plugin path, where the framework error handler catches the exception.

Exploits (1)

github STUB 1 stars
by HermesNA-1 · pythonpoc
https://github.com/HermesNA-1/SnakeSploit/tree/main/data/modules_generated/cve-2026-14181_fastifymiddie_versions_910.py

This repository contains an auto-generated stub module for CVE-2026-14181, a vulnerability in @fastify/middie versions 9.1.0 through 9.3.2. The module includes placeholder code for probing target connectivity but lacks actual exploit implementation for the URL normalization flaw.

Classification
Stub 99%
Attack Type
Other
Complexity
Moderate
Reliability
Theoretical
Target: @fastify/middie versions 9.1.0 through 9.3.2
No auth needed
Prerequisites: Network access to the target service · Target must be running a vulnerable version of @fastify/middie
mistral-large-3 · analyzed Jul 09, 2026 Full analysis →

Scores

CVSS v3 7.5
EPSS 0.0029
EPSS Percentile 21.4%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CISA SSVC

Vulnrichment
Exploitation none
Automatable yes
Technical Impact partial

Details

CWE
CWE-248
Status published
Products (3)
@fastify/middie/@fastify/middie 9.1.0 - 9.3.3
@fastify/middie/@fastify/middie 9.3.3
fastify/fastify\/middie 9.1.0 - 9.3.3
Published Jul 01, 2026
Tracked Since Jul 01, 2026