What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-02 · updated 2026-10-06
• Weakness: CWE-770

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 products

• better-auth: before 1.4.2 — fixed in 1.4.2

How to fix

Upgrade to a fixed version: better-auth 1.4.2. Check the vendor advisory for mitigations.

References

• https://github.com/better-auth/better-auth/security/advisories/GHSA-569q-mpph-wgww
• https://www.vulncheck.com/advisories/better-auth-before-basepath-modification-dos

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