CVE-2026-53512 – Better Auth: OAuth refresh-token replay via missing client authentication on oidc-provider and mcp plugins

CVE ID :CVE-2026-53512

Published : July 15, 2026, 5:18 p.m. | 16 minutes ago

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.

Severity: 0.0 | NA

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