CVE-2026-64645

About vulnerability

Impact

A rewrites() or redirects() rule that builds its external destination hostname from request-controlled input can be pointed at an arbitrary hostname, regardless of the rule’s hostname suffix. For a rewrite, Next.js proxies the request to that arbitrary host and serves the response from the application’s origin, leading to Server-Side Request forgery. A redirects() rule configured this way is vulnerable to an Open Redirect.

This affects any destination that puts a dynamic segment in the hostname, whether from the path:

// next.config.js
module.exports = {
async rewrites() {
return [
{
source: '/:tenant',
destination: 'https://:tenant.api.example.com',
},
]
},
}

or from a has capture:

// next.config.js
module.exports = {
async rewrites() {
return [
{
source: '/',
has: [{ type: 'query', key: 'region', value: '(?<region>.+)' }],
destination: 'https://:region.api.example.com',
},
]
},
}

Workarounds

If you cannot upgrade immediately, do not build the hostname of an external rewrites() or redirects() destination from user-controlled input. If a dynamic subdomain is required, constrain the value to hostname-safe characters: value: '(?<region>[a-z0-9-]+)'.

Affected product:

Next.js , React , braintrust-openai-agents , braintrust-otel , braintrust-sdk-javascript , braintrust-temporal , bufbuild/connect-es , create-next-app , expo-next-adapter , lit-labs-nextjs , mastra-braintrust , mui-material-nextjs , orama-orama , pigment-css , sb , sentry-nextjs , storybook , storybook-addon-a11y , storybook-addon-actions , storybook-addon-backgrounds , storybook-addon-controls , storybook-addon-docs , storybook-addon-essentials , storybook-addon-highlight , storybook-addon-interactions , storybook-addon-links , storybook-addon-measure , storybook-addon-outline , storybook-addon-themes , storybook-addon-toolbars , storybook-addon-viewport , storybook-angular , storybook-blocks , storybook-builder-manager , storybook-builder-vite , storybook-builder-webpack5 , storybook-channel-postmessage , storybook-channels , storybook-cli , storybook-client-logger , storybook-codemod , storybook-components , storybook-core-client , storybook-core-common , storybook-core-events , storybook-core-server , storybook-core-webpack , storybook-csf-plugin , storybook-csf-tools , storybook-docs-tools , storybook-ember , storybook-html , storybook-html-vite , storybook-html-webpack5 , storybook-instrumenter , storybook-manager , storybook-manager-api , storybook-nextjs , storybook-node-logger , storybook-preact , storybook-preact-vite , storybook-preact-webpack5 , storybook-preset-create-react-app , storybook-preset-html-webpack , storybook-preset-preact-webpack , storybook-preset-react-webpack , storybook-preset-server-webpack , storybook-preset-svelte-webpack , storybook-preset-vue3-webpack , storybook-preview , storybook-preview-api , storybook-react , storybook-react-dom-shim , storybook-react-vite , storybook-react-webpack5 , storybook-router , storybook-server , storybook-server-webpack5 , storybook-svelte , storybook-svelte-vite , storybook-svelte-webpack5 , storybook-sveltekit , storybook-telemetry , storybook-theming , storybook-types , storybook-vue3 , storybook-vue3-vite , storybook-vue3-webpack5 , storybook-web-components , storybook-web-components-vite , storybook-web-components-webpack5

Affected packages:

create-next-app @ 12.3.7 (+723 more)