Vulnerability Description
Better Auth is an authentication and authorization library for TypeScript. From 1.6.0 until 1.6.11, the @better-auth/oauth-provider POST /oauth2/token endpoint for the authorization_code grant redeems a single-use authorization code through a non-atomic find-then-delete sequence, allowing two concurrent requests to pass the read step and mint independent access tokens, refresh tokens, and ID tokens; legacy /oauth2/token and /mcp/token paths in oidc-provider and mcp plugins share the same primitive. 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 | >= 1.6.0, < 1.6.11 |
Related Weaknesses (CWE)
References
- https://github.com/better-auth/better-auth/commit/b4bc65a007784b2eb0efb459e5fa6fPatch
- https://github.com/better-auth/better-auth/releases/tag/v1.6.11Release Notes
- https://github.com/better-auth/better-auth/security/advisories/GHSA-7w99-5wm4-3gMitigationVendor Advisory
FAQ
What is CVE-2026-53518?
CVE-2026-53518 is a vulnerability with a CVSS score of 8.1 (HIGH). Better Auth is an authentication and authorization library for TypeScript. From 1.6.0 until 1.6.11, the @better-auth/oauth-provider POST /oauth2/token endpoint for the authorization_code grant redeems...
How severe is CVE-2026-53518?
CVE-2026-53518 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-2026-53518?
Check the references section above for vendor advisories and patch information. Affected products include: Better-Auth Better-Auth\/Oauth-Provider, Better-Auth Better Auth.