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Vulnerability record · CVE-2025-71401 · published 2 August 2026

CVE-2025-71401: Allocation without limits vulnerability

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 4.0 Critical EPSS 0.46% · top 63.0% CWE-770 · Allocation without limits Deferred
9.3CVSS 4.0 base score
0.46%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
2References
8 Sep 2026Last modified by NVD

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.

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:

References

LinkTags
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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Source: NIST National Vulnerability Database (record CVE-2025-71401), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.