diff --git a/.changeset/rich-spoons-fold.md b/.changeset/rich-spoons-fold.md
new file mode 100644
index 000000000000..217562a24ce8
--- /dev/null
+++ b/.changeset/rich-spoons-fold.md
@@ -0,0 +1,5 @@
+---
+"astro": patch
+---
+
+Fixes assets endpoint in serverless returning 404 in certain situations where the website might be under a protected route
diff --git a/packages/astro/src/assets/endpoint/generic.ts b/packages/astro/src/assets/endpoint/generic.ts
index 22b15446da75..5c51f6575534 100644
--- a/packages/astro/src/assets/endpoint/generic.ts
+++ b/packages/astro/src/assets/endpoint/generic.ts
@@ -7,9 +7,12 @@ import { isRemoteAllowed } from '../utils/remotePattern.js';
 // @ts-expect-error
 import { imageConfig } from 'astro:assets';
 
-async function loadRemoteImage(src: URL) {
+async function loadRemoteImage(src: URL, headers: Headers) {
 	try {
-		const res = await fetch(src);
+		const res = await fetch(src, {
+			// Forward all headers from the original request
+			headers,
+		});
 
 		if (!res.ok) {
 			return undefined;
@@ -41,15 +44,16 @@ export const GET: APIRoute = async ({ request }) => {
 
 		let inputBuffer: ArrayBuffer | undefined = undefined;
 
-		const sourceUrl = isRemotePath(transform.src)
+		const isRemoteImage = isRemotePath(transform.src);
+		const sourceUrl = isRemoteImage
 			? new URL(transform.src)
 			: new URL(transform.src, url.origin);
 
-		if (isRemotePath(transform.src) && isRemoteAllowed(transform.src, imageConfig) === false) {
+		if (isRemoteImage && isRemoteAllowed(transform.src, imageConfig) === false) {
 			return new Response('Forbidden', { status: 403 });
 		}
 
-		inputBuffer = await loadRemoteImage(sourceUrl);
+		inputBuffer = await loadRemoteImage(sourceUrl, isRemoteImage ? new Headers() : request.headers);
 
 		if (!inputBuffer) {
 			return new Response('Not Found', { status: 404 });