CVE-2025-71401Public exploitNetwork attack vector

Service interruption via forwarded-header base-path poisoning

Published Aug 2, 2026 · Updated Aug 2, 2026

Denial of service in Better Auth before 1.4.2 allows remote attackers to interrupt authentication routing via a crafted first request. When baseURL is unset, initialization trusts forwarded host and protocol headers, derives basePath from the resulting URL, and retains the attacker-controlled path. The request must arrive first after startup; successful poisoning makes every authentication route return 404 until restart, while explicit baseURL configuration prevents reachability.

CVSS severity9.3
Critical
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Denial of service in Better Auth before 1.4.2 allows remote attackers to interrupt authentication routing via a crafted first request. When baseURL is unset, initialization trusts forwarded host and protocol headers, derives basePath from the resulting URL, and retains the attacker-controlled path. The request must arrive first after startup; successful poisoning makes every authentication route return 404 until restart, while explicit baseURL configuration prevents reachability.

The record

CVE
CVE-2025-71401
Published
Aug 2, 2026
Updated
Aug 2, 2026
Vendor
Better Auth
Product
Better Auth
Classifications
CWE-73, CWE-770, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <1.4.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Better Auth · Better Authversion=0 <1.4.1

Published CVSS scores

2.9GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
9.3VulnCheck CNACVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
5.9VulnCheck CNACVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-73External Control of File Name or Path
CWE-770Allocation of Resources Without Limits or Throttling
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo