Vulnerability in @Better-Auth Oauth-Provider
CVE-2026-53517
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.
Vulnerability class: Race Condition
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (35.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 35th percentile — 35.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- @Better-Auth Oauth-Provider — versions >= 1.6.0, < 1.6.11
- Better-Auth — versions >= 1.4.8-beta.7, < 1.6.0
- Better-Auth Better Auth — versions 1.4.8
- Better-Auth Better-Auth\/oauth-Provider
Weakness classification (CWE)
References
- github.com/better-auth/better-auth/security/advisories/GHSA-392p-2q2v-4372 (Mitigation, Vendor Advisory)
- github.com/better-auth/better-auth/commit/c6918ecc9e3a75892169415d7f6c95b591b6a… (Patch)
- github.com/better-auth/better-auth/releases/tag/v1.6.11 (Release Notes)
Frequently asked questions
- What is CVE-2026-53517?
- CVE-2026-53517 is a high-severity vulnerability in @Better-Auth Oauth-Provider, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 8.1/10. Published 2026-07-15.
- How severe is CVE-2026-53517?
- High severity. CVSS v3 base score is 8.1 out of 10.