What’s Vulnerable › Vulnerabilities

CVE-2026-53517: Better Auth OAuth Provider: Refresh Token Rotation Race Condition Allows Concurrent Replay and Token Family Forking

• Severity: high (CVSS 8.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-15 · updated 2026-07-21
• Weakness: CWE-362

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.

Affected products

• Better-Auth/Oauth-Provider: from 1.6.0 before 1.6.11 — fixed in 1.6.11
• better-auth: from 1.4.9 before 1.6.11; 1.4.8, 1.4.8-beta7 — fixed in 1.6.11

How to fix

Upgrade to a fixed version: Better-Auth/Oauth-Provider 1.6.11; better-auth 1.6.11. Check the vendor advisory for mitigations.

References

• https://github.com/better-auth/better-auth/commit/c6918ecc9e3a75892169415d7f6c95b591b6a52d
• https://github.com/better-auth/better-auth/releases/tag/v1.6.11
• https://github.com/better-auth/better-auth/security/advisories/GHSA-392p-2q2v-4372

Get alerted when CVE-2026-53517 or the next vulnerability affects your stack