Fix Improper Error Handling in SvelteKit
Leaking stack traces or database internals is a gift to any adversary. In SvelteKit, improper error handling in +page.server.js or +server.js routes often exposes sensitive environment variables, query structures, or logic paths. If you're throwing raw Error objects, you're leaking recon data. Secure implementations must distinguish between 'expected' errors (4xx) and 'unexpected' failures (5xx), ensuring the client only sees sanitized metadata.
The Vulnerable Pattern
// src/routes/api/data/+server.js import { json } from '@sveltejs/kit'; import { db } from '$lib/database';
export async function GET({ url }) { try { const id = url.searchParams.get(‘id’); const result = await db.query(SELECT * FROM secrets WHERE id = ${id}); return json(result); } catch (err) { // VULNERABILITY: This leaks the raw SQL error message and stack trace to the client return new Response(JSON.stringify({ error: err.message, stack: err.stack }), { status: 500 }); } }
The Secure Implementation
The vulnerable code manually stringifies the Error object, exposing the database driver's internal state. The secure version leverages SvelteKit's built-in 'error' helper. When an unexpected error is thrown, SvelteKit automatically masks the message in production to 'Internal Error' unless it is an instance of the Kit error class. Furthermore, implementing the 'handleError' hook in 'hooks.server.js' allows you to intercept these failures, log the sensitive details to a secure sink (like Sentry or CloudWatch), and return a sanitized deconfliction ID to the user.
// src/routes/api/data/+server.js import { error, json } from '@sveltejs/kit'; import { db } from '$lib/database'; import { logger } from '$lib/logger';export async function GET({ url }) { const id = url.searchParams.get(‘id’);
try { const result = await db.getUserSecret(id); // Use parameterized queries inside if (!result) throw error(404, 'Not Found'); return json(result); } catch (err) { // Log the actual error internally for debugging logger.error('Database query failed', { error: err.message, id }); // SvelteKit's error() helper sanitizes the response for the client // In production, unexpected errors are automatically masked throw error(500, { message: 'An internal server error occurred', referenceId: 'ERR_QUERY_001' }); }
}
Your SvelteKit API
might be exposed to Improper Error Handling
74% of SvelteKit apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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