CVE-2025-71401: Better-Auth

Medium severity, CVSS 5.9. EPSS: 0.5% chance of exploitation in the next 30 days.

better-auth (npm) before 1.4.2 allows an external request to configure baseURL when it is not otherwise defined (e.g., BETTER_AUTH_URL is unset). An attacker able to make the very first request to the server after startup can poison the router's base path, causing all routes to return 404 for all users (denial of service). The issue is not reachable when baseURL is explicitly configured or on typical managed hosting platforms.

Affected products

• Better-Auth Better-Auth: before 1.4.2 (fixed in 1.4.2)

Published 2026-08-02. Last modified 2026-10-06.