Vulnerability · Published Aug 2, 2026 · Assigned by VulnCheck

CVE-2025-71401better-auth before 1.4.2 basePath Modification DoS

Medium 5.9

In plain English

A medium-severity resource allocation without limits in better-auth from better-auth. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.9Medium

Exploit odds (30 days)0.5%top 60.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	better-auth	1.4.2	GHSA-569q-mpph-wgww

Affected products (as reported)

Vendor	Product	Versions
better-auth	better-auth	0 – before 1.4.2

Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

References

GitHub Security Advisory (GHSA-569q-mpph-wgww) vendor-advisory
VulnCheck Advisory: better-auth before 1.4.1 basePath Modification DoS third-party-advisory