Description
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.
Metrics
CVSS 3.1 9.1/10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NWeakness enumeration
Affected software
| Vendor | Product | Versions |
|---|---|---|
| better-auth | better-auth | < 1.6.11 |
References
- https://github.com/better-auth/better-auth/commit/1f2ff4215c4affff0b140b0c0a712c0dde35659cPatch
- https://github.com/better-auth/better-auth/pull/9576Issue Tracking, Patch
- https://github.com/better-auth/better-auth/releases/tag/v1.6.11Release Notes
- https://github.com/better-auth/better-auth/security/advisories/GHSA-pw9m-5jxm-xr6hMitigation, Vendor Advisory
Timeline
- Published
- Jul 15, 2026
- Last modified
- Jul 21, 2026
- NVD status
- Analyzed