CVE-2025-71401
Startup-request baseURL poisoning in better-auth allows site-wide 404 DoS
Is CVE-2025-71401 being exploited?
Not confirmed. CVE-2025-71401 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.26% probability of exploitation in the next 30 days.
How severe is CVE-2025-71401?
CVE-2025-71401 is rated Critical with a CVSS score of 9.3. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2025-71401?
Yes. A fix has been recorded for CVE-2025-71401. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2025-71401 affect?
CVE-2025-71401 affects better-auth <1.4.2 (npm), Node.js apps using better-auth without BETTER_AUTH_URL, Self-hosted servers where env var is unset. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2025-71401?
Upgrade to better-auth >=1.4.2 or set BETTER_AUTH_URL env var and restart services
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated attacker making first request after startup can poison baseURL, causing all routes to return 404 (Denial of Service).
Immediate action required
- affected< 1.4.2
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.