Incorrect Authorization Affecting better-auth package, versions <1.6.11
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published8 Jul 2026
- disclosed7 Jul 2026
- creditsubhan umer
Introduced: 7 Jul 2026
CVE-2026-53512 (opens in a new tab)How to fix?
Upgrade better-auth to version 1.6.11 or higher.
Overview
better-auth is a The most comprehensive authentication library for TypeScript.
Affected versions of this package are vulnerable to Incorrect Authorization in the refresh_token grant process of the legacy oidcProvider and mcp plugins, where confidential clients are not required to authenticate using their client_secret. An attacker can gain unauthorized access to user resources and impersonate confidential clients by obtaining a valid refresh_token and the associated public client_id. This allows indefinite minting of access tokens and refresh tokens until the chain is revoked or expires.
** Note:** This is only exploitable if the application uses either the oidcProvider or mcp plugins with at least one confidential OAuth client registered and does not enforce PKCE for all clients.
Workaround
This vulnerability can be mitigated by migrating to @better-auth/oauth-provider, forcing all clients to public with PKCE, restricting token endpoints to known client IPs at the network layer, performing out-of-band refresh-token rotation, or narrowing the CORS allowlist for the affected endpoints.