Overview
About vulnerability
Impact
fast-uri canonicalizes a host to its ASCII form only when the input carries an explicit scheme. When resolve() resolves a scheme-relative reference (//host/) against a scheme-bearing base, it still emits the host verbatim even though the effective scheme is known, so re-parsing the resolved URI yields a different host than the one resolve() returned. An application that resolves an untrusted reference with fast-uri and then checks or routes on the resulting host can make a policy decision on one host and reach another. This is an incomplete-fix variant of CVE-2026-13676, whose IDN canonicalization was applied only to the scheme-bearing form.
Patches
Upgrade to fast-uri 2.4.5, 3.1.6, or 4.1.3. resolve() now canonicalizes the host once the effective scheme is known, and fails closed if a raw non-ASCII host cannot be converted.
Workarounds
Resolve scheme-relative references against a base that carries a scheme before performing any host-policy or origin check.
Details
- Affected product:
- AngularJS , Fastify , Node.js , React , Vue , ajv , ajv-compiler , ajv-draft-04 , ajv-errors , ajv-formats , ajv-keywords , api-extractor-model , babel-loader , cache-loader , css-loader , css-minimizer-webpack-plugin , devkit , esbuild-loader , extract-css-chunks-webpack-plugin , fast-json-stringify , fast-json-stringify-compiler , fast-uri , file-loader , fork-ts-checker-webpack-plugin , friendly-errors-webpack-plugin , hard-source-webpack-plugin , html-webpack-plugin , light-my-request , mini-css-extract-plugin , minimizer-webpack-plugin , nuxt , optimize-css-assets-webpack-plugin , postcss-loader , rushstack , schema-utils , style-resources-loader , table , thread-loader , time-fix-plugin , ts-command-line , tsdoc , url-loader , webpack , webpack-dev-middleware , webpack-dev-server , webpackbar , worker-loader
- Affected packages:
- fastify @ 4.29.1 (+456 more)