CVE-2026-53512 Better Auth: OAuth refresh-token replay via missing client authentication on oidc-provider and mcp plugins
Attackers can replay OAuth refresh tokens to mint access tokens because the oidc-provider and mcp plugins fail to verify client secrets.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53512?
CVE-2026-53512 is a critical authentication bypass vulnerability in better-auth, published on 15 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-53512?
2 open source packages ship an affected version, including better-auth. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
better-auth npm | All versions | 1.6.11 |
better-auth npm | All versions | 1.6.11 |
Products include Better-Auth Better Auth.
How do I fix CVE-2026-53512?
Upgrade better-auth to 1.6.11 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-53512 being exploited?
There is no known exploitation of CVE-2026-53512 in the wild and no public exploit code.
Other vulnerabilities in better-auth
- CVE-2026-53516 Better Auth: Account takeover via OAuth auto-link to unverified pre-registered email
- CVE-2024-56734 Better Auth has an Open Redirect Vulnerability in Verify Email Endpoint
- CVE-2026-53514 Better Auth: Unauthorized invitation acceptance via unverified email match in organization plugin
- CVE-2026-45337 Better Auth: Device authorization approve and deny accept any authenticated session while the user code is pending
- CVE-2025-27143 Beter Auth has an Open Redirect via Scheme-Less Callback Parameter
Sources
Also known as GHSA-pw9m-5jxm-xr6h.