CVE-2026-53517
Received Received - Intake

Race Condition in Better Auth OAuth Token Refresh

Publication date: 2026-07-15

Last updated on: 2026-07-15

Assigner: GitHub, Inc.

Description
Better Auth is an authentication and authorization library for TypeScript. From 1.4.8-beta.7 until 1.6.11, the @better-auth/oauth-provider POST /oauth2/token endpoint on the refresh_token grant performs a non-atomic read, validate, revoke, and mint sequence on the oauthRefreshToken row, allowing concurrent requests with the same parent refresh token to pass the revoked check and create forked refresh-token families; the vulnerable range also includes embedded better-auth plugin versions before 1.6.0. This issue is fixed in version 1.6.11.

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Meta Information

Published
2026-07-15
Last Modified
2026-07-15
Generated
2026-07-15
AI Q&A
2026-07-15
EPSS Evaluated
N/A
NVD
CVE-2026-53517
EUVD
EUVD-2026-44745

Affected Vendors & Products

Showing 7 associated CPEs
Vendor Product Version / Range
better_auth better_auth From 1.4.8-beta.7 (inc) to 1.6.11 (inc)
better_auth better_auth to 1.6.0 (exc)
better-auth better-auth From 1.4.8-beta.7 (inc) to 1.6.11 (inc)
better-auth better-auth to 1.6.0 (exc)
better-auth better-auth 1.6.11
better-auth oauth-provider to 1.6.11 (exc)
better-auth oauth-provider to 1.6.0 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-362 The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
CWE-367 The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.

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Executive Summary

CVE-2026-53517 is a race condition vulnerability in Better Auth's OAuth provider affecting versions before 1.6.11. It occurs in the refresh token rotation process where concurrent requests using the same parent refresh token can both pass validation before either revokes it, creating multiple valid refresh token families. This violates RFC 9700 requirements for token invalidation.

Impact Analysis

This vulnerability allows attackers to gain indefinite unauthorized access through stolen refresh tokens until revocation or expiration. Legitimate users may also bypass detection due to forked token families. The impact includes potential data breaches, unauthorized actions, and compromised system integrity.

Compliance Impact

This vulnerability likely violates compliance requirements for access control and data protection. GDPR requires proper user authentication and access revocation mechanisms. HIPAA mandates secure authentication and authorization controls. The indefinite access risk conflicts with both standards' data protection principles.

Detection Guidance

Detecting this vulnerability requires checking the version of the @better-auth/oauth-provider package or embedded OAuth plugin in your system. If you are using a version before 1.6.11 for the package or before 1.6.0 for the embedded plugin, your system is vulnerable. Run commands like 'npm list @better-auth/oauth-provider' or check your package.json to verify the installed version.

Mitigation Strategies

Immediately upgrade to version 1.6.11 or later for the @better-auth/oauth-provider package, or 1.6.0 or later for the embedded OAuth plugin. If upgrading is not immediately possible, consider disabling refresh tokens entirely or reducing token lifetimes as temporary workarounds. Ensure database-level isolation and client-side serialization are implemented to reduce the risk of concurrent token operations.

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