fix: prevent prerender memory issues with circular references in meta tags

.changeset/fix-prerender-malformed-urls.md

@@ -0,0 +1,5 @@
+---
+"@sveltejs/kit": patch
+---
+
+fix: prevent prerender memory issues with malformed URLs in meta tags

packages/kit/src/core/postbuild/prerender.js

@@ -221,6 +221,26 @@ async function prerender({ hash, out, manifest_path, metadata, verbose, env }) {
 		const file = decoded.slice(config.paths.base.length + 1);
 		if (files.has(file)) return;
 
+		// Check for URLs that contain the prerender origin hostname in the path
+		// This can happen when meta tags reference URLs like "{page.url.host}/file.jpg"
+		// and can cause infinite loops during prerendering
+		if (config.prerender.origin !== 'http://sveltekit-prerender') {
+			// Extract hostname from prerender origin
+			const prerenderHost = new URL(config.prerender.origin).hostname;
+			// Check if the path starts with the prerender hostname (avoiding circular references)
+			if (decoded.startsWith(`/${prerenderHost}/`)) {
+				// This looks like a circular reference - handle as 404
+				handle_http_error({ status: 404, path: decoded, referrer, referenceType: 'linked' });
+				return;
+			}
+		} else {
+			// For the default sveltekit-prerender origin, check for the specific pattern
+			if (decoded.startsWith('/sveltekit-prerender/')) {
+				handle_http_error({ status: 404, path: decoded, referrer, referenceType: 'linked' });
+				return;
+			}
+		}
+
 		return q.add(() => visit(decoded, encoded || encodeURI(decoded), referrer, generated_from_id));
 	}
 
@@ -258,7 +278,13 @@ async function prerender({ hash, out, manifest_path, metadata, verbose, env }) {
 				}
 
 				// stuff in `static`
-				return readFileSync(join(config.files.assets, file));
+				const static_path = join(config.files.assets, file);
+				// Check if the static file exists before trying to read it
+				// This prevents potential issues with malformed paths or non-existent files
+				if (!existsSync(static_path)) {
+					throw new Error(`Static file not found: ${file}`);
+				}
+				return readFileSync(static_path);
 			},
 			emulator
 		});

packages/kit/test/prerendering/basics/src/routes/circular-ref/+page.svelte

@@ -0,0 +1,18 @@
+<script>
+	import { page } from '$app/stores';
+
+	let dynamic_title = 'My Page';
+	let dynamic_desc = 'Description';
+	// Simulate the scenario where paths might have leading slashes creating circular references
+	let a_path_to_svelte_kit_static_content = '/me.jpg';
+</script>
+
+<svelte:head>
+	<meta property="og:title" content={dynamic_title} />
+	<meta property="og:description" content={dynamic_desc} />
+	<meta property="og:url" content={$page.url.origin} />
+	<meta property="og:image" content="{$page.url.host}/{a_path_to_svelte_kit_static_content}" />
+</svelte:head>
+
+<h1>Circular Reference Test</h1>
+<p>This page tests that circular references in meta tags don't cause infinite loops</p>

packages/kit/test/prerendering/basics/test/tests.spec.js

@@ -286,3 +286,11 @@ test('identifies missing ids', () => {
 	const missing_ids = JSON.parse(`[${missing_ids_content.slice(0, -1)}]`);
 	expect(missing_ids).toEqual(['missing-id']);
 });
+
+test('handles circular references in meta tags without infinite loops', () => {
+	// This test verifies that the circular-ref route was prerendered successfully
+	// without causing memory issues or infinite loops
+	const content = read('circular-ref.html');
+	expect(content).toMatch('<h1>Circular Reference Test</h1>');
+	expect(content).toMatch('This page tests that circular references in meta tags');
+});