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fix(@angular/build): add host validation to internal SSR middleware #33674

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fix(@angular/build): add host validation to internal SSR middleware #33674

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17 changes: 17 additions & 0 deletions packages/angular/build/src/tools/vite/middlewares/ssr-middleware.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,9 @@ export function createAngularSsrInternalMiddleware(
): Connect.NextHandleFunction {
let cachedAngularServerApp: ReturnType<typeof getOrCreateAngularServerApp> | undefined;

const { allowedHosts } = server.config.server;
const disableAllowedHostsCheck = allowedHosts === true;

return function angularSsrMiddleware(
req: Connect.IncomingMessage,
res: ServerResponse,
Expand Down Expand Up @@ -62,6 +65,20 @@ export function createAngularSsrInternalMiddleware(
const webReq = new Request(createWebRequestFromNodeRequest(req), {
signal: AbortSignal.timeout(30_000),
});

if (!disableAllowedHostsCheck && Array.isArray(allowedHosts) && allowedHosts.length > 0) {
const { hostname } = new URL(webReq.url);
const isAllowed = allowedHosts.some(
(host) => hostname === host || hostname.endsWith(`.${host}`),
);
Comment on lines +71 to +73

@gemini-code-assist gemini-code-assist Bot Jul 29, 2026

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high

The current host matching logic has two issues:

  1. If an allowed host starts with a dot (e.g., .example.com to allow subdomains), hostname.endsWith(.${host}) evaluates to hostname.endsWith('..example.com'), which will fail to match subdomains.
  2. If an allowed host does not start with a dot (e.g., example.com), hostname.endsWith(.${host}) will match subdomains (e.g., sub.example.com), which is over-permissive and violates standard host matching behavior where subdomains are only allowed if a leading dot is explicitly specified.

We should update the matching logic to correctly handle leading dots, consistent with Vite and webpack-dev-server standards.

        const isAllowed = allowedHosts.some((host) => {
          if (host.startsWith('.')) {
            return hostname === host.slice(1) || hostname.endsWith(host);
          }
          return hostname === host;
        });

if (!isAllowed) {
res.statusCode = 400;
res.end('Bad Request: Host not allowed.');

return;
}
}

const webRes = await angularServerApp.handle(webReq);
if (!webRes) {
return next();
Expand Down
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