---
id: CVE-2026-110725
aliases:
  - GHSA-333x-w4r6-6crp
title: >-
  fast-uri vulnerable to scheme injection via an unescaped first-segment colon
  in suffix references
summary: >-
  fast-uri vulnerable to scheme injection via an unescaped first-segment colon
  in suffix references
severity: low
cvss: 3.7
cwe:
  - CWE-41
  - CWE-116
  - CWE-79
vendor: fast-uri
product: fast-uri
ecosystem: npm
affected:
  - fast-uri < 2.4.8
  - 'fast-uri >= 3.0.0, < 3.1.9'
  - 'fast-uri >= 4.0.0, < 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: '2026-10-23T21:36:41Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-333x-w4r6-6crp'
references:
  - url: >-
      https://github.com/fastify/fast-uri/security/advisories/GHSA-333x-w4r6-6crp
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-110725'
  - url: >-
      https://github.com/fastify/fast-uri/commit/39e6493c1356f30a0084171627eb266786e1620e
  - url: >-
      https://github.com/fastify/fast-uri/commit/a9b8d67353630aab053cd727cf629023dd018d2b
  - 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-333x-w4r6-6crp'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-110725.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-110725'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2556007'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-110725'
tags:
  - ghsa
  - npm
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00302
epssPercentile: 0.22817
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-20T19:14:33.067016Z'
ingestedAt: '2026-10-20T07:55:43.639Z'
---

## Overview

### Impact

`fast-uri`'s `serialize()`, `normalize()`, and `resolve()`, when called with the non-default option `reference: 'suffix'` on a reference that has no authority, emit a relative reference whose first path segment contains a bare colon without escaping it. RFC 3986 section 3.3 requires the first segment of a `path-noscheme` reference not to contain a colon, precisely because a bare colon makes the string reparse as an absolute URI with a scheme. `fast-uri`'s default serialization escapes that colon, but the suffix path does not.

For example, `normalize('javascript:alert(1)', { reference: 'suffix' })` returns `javascript:alert(1)`, which reparses as a live `javascript:` scheme; `data:` and `vbscript:` behave the same.

Applications that serialize or normalize a relative reference with `reference: 'suffix'` and then treat the result as a URI can turn inert input into a live `javascript:`, `data:`, or `vbscript:` URL (a cross-site scripting vector), and `equal()` can conflate a scheme-bearing reference with a relative one. Exposure is limited to applications that use the non-default `reference: 'suffix'` option.

### Patches

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

### Workarounds

Do not use the `reference: 'suffix'` option on untrusted input. If suffix output is required, percent-encode a colon in the first path segment of the result before treating it as a URI.

## Affected packages

- `fast-uri < 2.4.8`
- `fast-uri >= 3.0.0, < 3.1.9`
- `fast-uri >= 4.0.0, < 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** · Low · 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-2026-110725.json)