Overview
About vulnerability
Impact
fast-uri v4.1.0 and earlier do not treat a literal backslash (U+005C) as an authority delimiter. Node’s native WHATWG URL (used by fetch(), undici, and Node’s http/https clients) normalizes \ to / for special schemes (http, https, ws, wss, ftp, file), so the two parsers extract different hosts from the same input string.
For example, http://evil.com\@allowed.com is treated by fast-uri as host allowed.com with userinfo evil.com\, while Node’s WHATWG URL parser and fetch() see host evil.com with path /@allowed.com.
Applications that use fast-uri to enforce host-based policy (allowlists, denylists, loopback/SSRF filtering, redirect validation, outbound proxy routing) before passing the same URL into Node’s URL or fetch() consumers see a policy/use desync and can be steered to an unintended destination, including cloud metadata endpoints, loopback, or internal hosts.
Patches
Upgrade to fast-uri v4.1.1, v3.1.4, or v2.4.3.
Workarounds
None. Upgrade to the patched version.
Details
- Affected product:
- Angular , AngularJS , Fastify , Next.js , Node.js , React , Vue , ajv , ajv-compiler , ajv-draft-04 , ajv-errors , ajv-formats , ajv-keywords , api-extractor-model , astro , babel-loader , cache-loader , css-loader , css-minimizer-webpack-plugin , db0 , devframe , devkit , devtools , drizzle-orm , esbuild-loader , expo , 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 , impound , light-my-request , mdx , mini-css-extract-plugin , minimizer-webpack-plugin , ng-packagr , nitro , nostics , nuxt , optimize-css-assets-webpack-plugin , pdfjs-dist , postcss-loader , prisma , progress-bar-webpack-plugin , rushstack , schema-utils , streams , style-resources-loader , stylelint , table , telemetry , thread-loader , time-fix-plugin , ts-command-line , tsdoc , tsup , typescript-sdk , uglifyjs-webpack-plugin , unctx , unimport , unplugin , unstorage , url-loader , vite , vite-dev-rpc , vite-hot-client , vite-plugin-checker , vite-plugin-inspect , vite-plugin-react , vite-plugin-vue , vite-plugin-vue-inspector , vite-plugin-vue-tracer , vitefu , webpack , webpack-dev-middleware , webpack-dev-server , webpack-subresource-integrity , webpackbar , worker-loader
- Affected packages:
- react-router @ 7.18.1 (+686 more)