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Better Auth\/oauth ProviderApplication · Better Auth

CVE-2026-41427

MEDIUM · 6.5 CVSS v3.1 Published 2026-04-24
Fix available
A fix is available. Upgrade to 1.6.5 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Better Auth is an authentication and authorization library for TypeScript. Prior to 1.6.5, the clientPrivileges option documents a create action, but the OAuth client creation endpoints did not invoke the hook before persisting new clients. Deployments that configured clientPrivileges to restrict client registration were not actually restricted — any authenticated user could reach the create endpoints and register an OAuth client with attacker-chosen redirect URIs and metadata. This vulnerability is fixed in 1.6.5.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Better Auth's OAuth client creation endpoints failed to invoke the clientPrivileges hook before persisting new clients, allowing any authenticated user to bypass configured restrictions and register OAuth clients with attacker-controlled redirect URIs and metadata. This authorization bypass affected all deployments using clientPrivileges to restrict client registration prior to version 1.6.5.

MitigationUpgrade to Better Auth version 1.6.5 or later, then verify that the clientPrivileges hook is now properly enforced for OAuth client creation endpoints.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Better Auth\/oauth ProviderApplication
Affected:>= 1.4.9, < 1.6.5= 1.4.8= 1.7.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Better Auth version
    Check your package.json or node_modules/better-auth/package.json for the installed version number
    Affected if version is >= 1.4.9 and < 1.6.5, or equals 1.4.8, or equals 1.7.0
  2. Confirm OAuth provider is in use
    Inspect your Better Auth configuration to see if the oauth provider plugin is initialized and exported
    Affected if OAuth provider is enabled and clients can be registered through the API
  3. Verify clientPrivileges hook configuration
    Search your codebase for clientPrivileges hook definition in your Better Auth configuration options
    Affected if clientPrivileges hook exists but may not be enforced on client creation endpoints
  4. Inspect OAuth client creation permissions
    Review API logs or application logs for OAuth client creation requests and check which authenticated users can invoke the endpoint
    Affected if Any authenticated user without proper clientPrivileges validation can create OAuth clients
  5. Audit existing OAuth clients for unauthorized redirect URIs
    Query your database for OAuth clients table and review redirect_uri values against expected legitimate URIs
    Affected if OAuth clients exist with redirect URIs that were not explicitly authorized through the clientPrivileges hook

You are affected if Better Auth version is in the vulnerable range and your deployment allows authenticated users to create OAuth clients without clientPrivileges hook validation.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.6.5 or later
Fixed in 1.6.5
Interim mitigation

Upgrade to Better Auth version 1.6.5 or later, then verify that the clientPrivileges hook is now properly enforced for OAuth client creation endpoints.

Recommended fix High confidence

1.6.5 or later

  1. Upgrade Better Auth to version 1.6.5 or later using your package manager (e.g., npm install better-auth@^1.6.5 or yarn add better-auth@^1.6.5)
  2. After upgrading, verify that the clientPrivileges option is properly configured in your authentication setup if you use it to restrict OAuth client registration
  3. Review existing OAuth client registrations in your application to detect any potentially unauthorized clients that may have been created during the vulnerable period
  4. Test the OAuth flow to confirm client creation is now properly restricted according to your clientPrivileges configuration
Caveat No breaking changes specifically mentioned for this security fix; standard regression testing of authentication flows is recommended

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Better Auth\/oauth Provider Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing3.0 h
  • Review / QA2.0 h
8.0 hours of engineering $1,390
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-41427 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
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  • Version or environment caveats, and links to real fixes
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