CVE-2026-53512

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

Published Jul 15, 2026 CVSS 4.0 · 9.1 Critical EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-pw9m-5jxm-xr6h Better Auth: OAuth refresh-token replay via missing client authentication on oidc-provider and mcp plugins
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Better-auth
Better-auth better Auth
Vendors & Products Better-auth
Better-auth better Auth
Type Values Removed Values Added
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.
Title Better Auth: OAuth refresh-token replay via missing client authentication on oidc-provider and mcp plugins
Weaknesses CWE-287
CWE-306
CWE-345
CWE-863
References
Metrics cvssV4_0

{'score': 9.1, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N'}

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jul 18, 2026, 1:08 AM
Reserved
Jun 9, 2026, 5:30 PM
Status
Analyzed
Published
Jul 15, 2026, 6:16 PM
Modified
Jul 21, 2026, 1:33 PM