---
id: CVE-2026-107832
title: fastify is a fast and low overhead web framework for Node.js
summary: >-
  fastify is a fast and low overhead web framework for Node.js. In versions
  5.12.2 through 5.12.5, the routine that lowercases header names declared in a
  route schema does not lowercase the enum or const header names nested inside a
  proper…
severity: low
cvss: 3.7
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N'
cwe:
  - CWE-178
published: '2026-10-13'
updated: '2026-10-13'
sourceUpdated: '2026-10-13T14:17:19.167'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-107832'
references:
  - url: 'https://cna.openjsf.org/security-advisories.html'
    label: ce714d77-add3-4f53-aff5-83d477b104bb
  - url: 'https://github.com/fastify/fastify/security/advisories/GHSA-389g-gv7q-r4x8'
    label: ce714d77-add3-4f53-aff5-83d477b104bb
tags:
  - nvd
ingestedAt: '2026-10-13T14:29:01.845Z'
---

## Overview

fastify is a fast and low overhead web framework for Node.js. In versions 5.12.2 through 5.12.5, the routine that lowercases header names declared in a route schema does not lowercase the enum or const header names nested inside a propertyNames subschema. As a result, a header allow-list or deny-list written with canonical (non-lowercase) casing never matches the incoming lowercased header, so a restricted header passes validation and reaches the route handler. An attacker can therefore bypass a case-sensitive header validation rule and smuggle a forbidden header past the schema, affecting the integrity of request handling. The issue is fixed in fastify 5.12.6, and users should upgrade to 5.12.6 or later. There is no workaround other than upgrading, though applications can declare header names in lowercase to avoid the mismatch.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.