Vulnerability 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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Better-Auth | Better-Auth\/Oauth-Provider | >= 1.6.0, < 1.6.11 |
| Better-Auth | Better Auth | >= 1.4.9, < 1.6.11 |
Related Weaknesses (CWE)
References
- https://github.com/better-auth/better-auth/commit/c6918ecc9e3a75892169415d7f6c95Patch
- https://github.com/better-auth/better-auth/releases/tag/v1.6.11Release Notes
- https://github.com/better-auth/better-auth/security/advisories/GHSA-392p-2q2v-43MitigationVendor Advisory
FAQ
What is CVE-2026-53517?
CVE-2026-53517 is a vulnerability with a CVSS score of 8.1 (HIGH). 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 perfor...
How severe is CVE-2026-53517?
CVE-2026-53517 has been rated HIGH with a CVSS base score of 8.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-53517?
Check the references section above for vendor advisories and patch information. Affected products include: Better-Auth Better-Auth\/Oauth-Provider, Better-Auth Better Auth.