CVE-2025-71401

critical · 9.3

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.

9.3

CVSS

0.3%

EPSS (exploit prob.)

18th

EPSS percentile

2026-08-02

Published

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Weaknesses

CWE-770

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

Query this programmatically:

curl https://evil-db.io/api/v1/cve/CVE-2025-71401