CVE-2026-53512 — Better Auth: OAuth refresh-token replay via missing client authentication on oidc-provider and mcp plugins
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_to…
Published: 2026-07-15 · CVSS: 9.1 · CVSS 4.0
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7