---
id: CVE-2026-84292
title: fast-uri serializes the port component of a URI without validating it
summary: >-
  fast-uri serializes the port component of a URI without validating it. When
  recomposing the authority, the userinfo and host components are escaped but
  the port is concatenated verbatim, so a port value that is not a sequence of
  digits c…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'
cwe:
  - CWE-116
vendor: openjsf
product: fast-uri
affected:
  - fast-uri < 2.4.6
  - 'fast-uri >= 3.0.0, < 3.1.7'
  - 'fast-uri >= 4.0.0, < 4.1.4'
patched:
  - fast-uri 4.1.4
published: '2026-09-02'
updated: '2026-09-28'
sourceUpdated: '2026-09-28T23:10:00.143'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-84292'
references:
  - url: 'https://cna.openjsf.org/security-advisories.html'
    label: ce714d77-add3-4f53-aff5-83d477b104bb
  - url: >-
      https://github.com/fastify/fast-uri/security/advisories/GHSA-qw65-cvwx-89v3
    label: ce714d77-add3-4f53-aff5-83d477b104bb
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-84292'
  - url: >-
      https://github.com/fastify/fast-uri/commit/820e8478dd7da3d09f187bfaf35d50b71f67b8b4
  - url: 'https://github.com/fastify/fast-uri/releases/tag/v2.4.6'
  - url: 'https://github.com/fastify/fast-uri/releases/tag/v3.1.7'
  - url: 'https://github.com/fastify/fast-uri/releases/tag/v4.1.4'
  - url: 'https://github.com/advisories/GHSA-qw65-cvwx-89v3'
tags:
  - nvd
  - ghsa
  - npm
aliases:
  - GHSA-qw65-cvwx-89v3
ecosystem: npm
ingestedAt: '2026-09-28T22:22:13.613Z'
---

## Overview

fast-uri serializes the port component of a URI without validating it. When recomposing the authority, the userinfo and host components are escaped but the port is concatenated verbatim, so a port value that is not a sequence of digits can inject authority delimiters, demoting the intended host to userinfo and pointing the authority at an attacker-controlled host. Both fast-uri and Node's URL read the result back as the attacker's host with no error, so re-validating the built URI does not catch it. This affects applications that build URIs from parts and assign untrusted data to the port component through the serialize, normalize, or equal functions in their object forms. The issue affects fast-uri versions before 2.4.6, from 3.0.0 before 3.1.7, and from 4.0.0 before 4.1.4. It is fixed in 2.4.6, 3.1.7, and 4.1.4, where recomposeAuthority rejects any port that is not a digit sequence per RFC 3986.

## Affected

- `fast-uri < 2.4.6`
- `fast-uri >= 3.0.0, < 3.1.7`
- `fast-uri >= 4.0.0, < 4.1.4`

## Remediation

Upgrade past the affected range:

- `fast-uri 4.1.4`

## Package advisory (CVE-2026-84292)

Affected packages:

- `fast-uri < 2.4.6`
- `fast-uri >= 3.0.0, < 3.1.7`
- `fast-uri >= 4.0.0, < 4.1.4`

Patched in:

- `fast-uri 2.4.6`
- `fast-uri 3.1.7`
- `fast-uri 4.1.4`

Source: https://github.com/advisories/GHSA-qw65-cvwx-89v3