critical9.1
CVE-2026-53512
Better Auth: OAuth refresh-token replay via missing client authentication on oidc-provider and mcp plugins
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | better-auth | < 1.6.11 | 1.6.11 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Better-Auth | Better Auth | before 1.6.11 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-pw9m-5jxm-xr6h
- https://github.com/better-auth/better-auth/security/advisories/GHSA-pw9m-5jxm-xr6h
- https://github.com/better-auth/better-auth/releases/tag/v1.6.11
- https://nvd.nist.gov/vuln/detail/CVE-2026-53512
- https://github.com/better-auth/better-auth/pull/9576
- https://github.com/better-auth/better-auth/commit/1f2ff4215c4affff0b140b0c0a712c0dde35659c