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Better AuthApplication

CVE-2026-53512

CRITICAL · 9.1 CVSS v3.1 Published 2026-07-15
Fix available
A fix is available. Upgrade to 1.6.11 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 5 weeks old

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 1.6.11, the legacy oidcProvider and mcp plugins expose OAuth token endpoints whose refresh_token grant authenticates only possession of the bound refreshToken row and matching client_id, without verifying the confidential client's client_secret, allowing an attacker with a valid refresh_token to mint access tokens and rotated refresh tokens through /api/auth/oauth2/token or /api/auth/mcp/token. The @better-auth/oauth-provider package is not affected. This issue is fixed in version 1.6.11.

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

The legacy oidcProvider and mcp plugins in Better Auth versions before 1.6.11 expose OAuth token endpoints (/api/auth/oauth2/token and /api/auth/mcp/token) that validate refresh tokens using only the refreshToken row and client_id, but fail to verify the confidential client's client_secret during the refresh_token grant flow, allowing token minting by any attacker possessing a valid refresh_token.

MitigationUpgrade Better Auth to version 1.6.11 or later to include the client_secret verification in the refresh_token grant flow for the legacy oidcProvider and mcp plugins.

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 AuthApplication
Affected:< 1.6.11

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
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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 package.json or run npm list better-auth to see the installed version of better-auth package
    Affected if Version is below 1.6.11 (e.g., 1.6.10, 1.6.0, etc.)
  2. Verify oidcProvider or mcp plugins are in use
    Inspect your Better Auth configuration file (typically auth.ts or auth.js) for imports and plugin registration such as oidcProvider() or mcp()
    Affected if Either the oidcProvider plugin or mcp plugin is registered in your auth configuration
  3. Confirm confidential client setup exists
    Review your OAuth client configuration where clients are defined - look for client_id and client_secret pairs representing confidential clients (as opposed to public clients)
    Affected if Confidential clients with client_secret are configured in your OAuth/OIDC client registry
  4. Check for exposure of vulnerable token endpoints
    Verify your application exposes /api/auth/oauth2/token or /api/auth/mcp/token endpoints (check your routing configuration or API gateway)
    Affected if Either /api/auth/oauth2/token or /api/auth/mcp/token endpoints are publicly accessible and handling refresh_token grant requests

You are affected if you are running Better Auth version below 1.6.11, have the oidcProvider or mcp plugin enabled, use confidential OAuth clients with client_secret, and expose the refresh_token grant endpoint.

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 1.6.11 or later
Fixed in 1.6.11
Interim mitigation

Upgrade Better Auth to version 1.6.11 or later to include the client_secret verification in the refresh_token grant flow for the legacy oidcProvider and mcp plugins.

Recommended fix High confidence

1.6.11

  1. Identify the current Better Auth version in your project (check package.json or package-lock.json)
  2. Run the package manager upgrade command: npm install [email protected] (or yarn add [email protected], or pnpm add [email protected])
  3. Verify the upgrade was successful by running npm list better-auth or checking package.json
  4. Test OAuth token refresh flows through the /api/auth/oauth2/token and /api/auth/mcp/token endpoints to confirm the client_secret validation is now enforced
  5. If using the legacy oidcProvider or mcp plugins, ensure they are updated to the patched version

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

Fix this in Better Auth Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
16.0 hours of engineering $2,760
Get the upgrade done

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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-2026-53512 in production — separate from our analysis above.

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What this is

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What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data