---
id: CVE-2026-110180
aliases:
  - GHSA-wjr9-j795-jxcr
title: >-
  fast-uri vulnerable to host confusion via unchecked WHATWG host
  canonicalization
summary: >-
  fast-uri vulnerable to host confusion via unchecked WHATWG host
  canonicalization
severity: medium
cvss: 4.8
cwe:
  - CWE-20
  - CWE-436
  - CWE-1286
vendor: fast-uri
product: fast-uri
ecosystem: npm
affected:
  - 'fast-uri >= 2.4.2, < 2.4.8'
  - 'fast-uri >= 3.1.3, < 3.1.9'
  - 'fast-uri >= 4.0.1, < 4.2.3'
patched:
  - fast-uri 2.4.8
  - fast-uri 3.1.9
  - fast-uri 4.2.3
published: '2026-10-23'
updated: '2026-10-23'
sourceUpdated: '2026-10-23T21:38:02Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-wjr9-j795-jxcr'
references:
  - url: >-
      https://github.com/fastify/fast-uri/security/advisories/GHSA-wjr9-j795-jxcr
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-110180'
  - url: >-
      https://github.com/fastify/fast-uri/commit/58c183d0b168ad87f98773266444ce1f6375803a
  - url: >-
      https://github.com/fastify/fast-uri/commit/ddfc6a51122dfce0365655f04479fc3adb7f6b3c
  - url: >-
      https://github.com/fastify/fast-uri/commit/f6d46dfeab025d0c440485f4ae29fa4f14707646
  - url: 'https://cna.openjsf.org/security-advisories.html'
  - url: 'https://github.com/fastify/fast-uri/releases/tag/v2.4.8'
  - url: 'https://github.com/fastify/fast-uri/releases/tag/v3.1.9'
  - url: 'https://github.com/fastify/fast-uri/releases/tag/v4.2.3'
  - url: 'https://github.com/advisories/GHSA-wjr9-j795-jxcr'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-110180.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-110180'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2556008'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-110180'
tags:
  - ghsa
  - npm
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00255
epssPercentile: 0.16981
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-20T16:06:29.053757Z'
ingestedAt: '2026-10-20T07:55:43.639Z'
---

## Overview

### Impact

`fast-uri` versions `>= 2.4.2, <= 2.4.7`, `>= 3.1.3, <= 3.1.8`, and `>= 4.0.1, <= 4.2.2` can silently rewrite the host of an HTTP-family URL (`http`, `https`, `ws`, `wss`, or any scheme with `domainHost: true`). For those schemes `canonicalizeHost()` passes the parsed host to the WHATWG `URL` parser and adopts its `.hostname` without checking that the parser read the whole input as a host. RFC 3986 permits `@` inside the host group and the WHATWG parser strips TAB, LF, and CR, so the authority `fast-uri` reports is rewritten by that second parser with no `error` set: data before an `@` is dropped and whitespace is removed.

For example, `fast-uri` parses `http://a@b@evil.example/` to host `evil.example` (dropping the `b` segment), and a host containing a raw TAB, CR, or LF has those characters stripped. `equal()` then treats a whitespace-smuggled host as the same as the clean one, and `resolve()` rewrites the authority the same way.

Applications that use `fast-uri` to enforce host-based policy (denylists, loopback filtering, redirect validation, outbound proxy routing) on one representation, such as the raw input, see a policy/use desync: the canonical host `fast-uri` returns differs from what was checked, and traffic can be steered to an unintended destination.

### Patches

Upgrade to `fast-uri` `2.4.8`, `3.1.9`, or `4.2.3`.

### Workarounds

Reject URIs whose authority contains more than one `@`, or contains TAB, CR, or LF, before calling `fast-uri`. Alternatively, treat any non-empty `parse(x).error` as fatal, and compare hosts only from the same `parse()` result.

## Affected packages

- `fast-uri >= 2.4.2, < 2.4.8`
- `fast-uri >= 3.1.3, < 3.1.9`
- `fast-uri >= 4.0.1, < 4.2.3`

## Remediation

Upgrade to a patched release:

- `fast-uri 2.4.8`
- `fast-uri 3.1.9`
- `fast-uri 4.2.3`

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Cost Management On Premise, Cryostat 4, Migration Toolkit for Applications 8, Multicluster Engine for Kubernetes, Network Observability Operator, OpenShift Lightspeed, … · no fix planned: Red Hat Ansible Automation Platform 2, Red Hat Directory Server 11, Red Hat Directory Server 12, Red Hat Openshift Data Foundation 4, … · updated 2026-10-20 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-110180.json)